genetics genetics-___________________ heredity-passing of traits from __________________________...
TRANSCRIPT
Genetics Genetics-___________________ Heredity-passing of traits
from __________________________
Trait- ____________________that can be passed on to
offspring ex: hair color, eye color, etc
Genes! Genes- _____________________
___________________________ __________________________ .
There are _________ of genes on each chromosome.
DNA chromosome gene protein trait
What Determines Traits?
Genes
Some traits are coded for by one gene which codes for one protein causing a trait. i.e. freckles, earlobe attachment, etc
protein
Polygenic Inheritance – When a Single Trait is Influenced by Many Genes
Height is a polygenic trait
Polygenic traits – ______________________________ _____________________________________________.
More than one gene = more than one protein that causes the trait so complex variation in that trait
Hand span, height, eye color, etc.
Chromosomes Homologous chromosomes-
________________________________________________________________________________________________________
One of each pair from Mom and one from Dad
Each human somatic (body) cell has _________ of homologous chromosomes
Other species have different numbers.
homologous chromosomes
Passing of One Gene Remember that during meiosis when we make
gametes (egg and sperm) the genetic material is cut in half.
Egg and sperm each only have ________________ because these gametes only get ONE copy of every chromosome (haploid).
When gametes come together during fertilization, it forms the baby with a complete set of chromosomes and ________________________ (_________).
Homologous Chromosomes
_____ contributed one and _____ contributed other of each pair of homologous chromosomes in our somatic cells.
Therefore, we received _______________ from each of our parents
This means each somatic cell has ________________ ____, and therefore, ______________.
Alleles Alleles - ________________________________
F allele codes for freckles f allele codes for no freckles
Allele for freckles--F
Allele for no freckles—f
Position on chromosomes where freckle presence gene is located
Genotype vs. Phenotype
Genotype- ______________________________________ Written as _________-one copy from each parent _________________
Phenotype- ____________________________________________
Written as _______________ Freckles or no freckles
***Phenotype = Genotype + Environment
Genotypes
_______________________ - (purebred) receiving two identical alleles for a particular trait from your parents. i.e. Freckle presence gene Alleles F=freckles and f=none Homozygous: FF or ff
______________________ - (hybrid) receiving two different alleles for a particular trait from your parents Heterozygous: ________?
F F F f f f
Mom Dad Mom Dad Mom Dad
Possibility #1 Possibility #2 Possibility #3
What About the Heterozygous Genotype?
FF genotype = ____________ phenotype? ff genotype = _____________phenotype? What about Ff phenotype? As it turns out, the allele coding for freckles, F,
___________________ the alleles coding for no freckles, f. The heterozygous genotype, Ff, results in
________________ ____________
_________________– form of trait that overcomes others and written as a ____________________________________- of trait that is hidden in the presence of a dominant one and written as a __________________
F F F f f f
Mom Dad Mom Dad Mom Dad
Genotype Example Phenotype
Homozygous Dominant
Freckles
No freckles
Heterozygous
So What? How can we use this information on meiosis
and genetics? If we know parents’ genotypes, we can figure
out the genotype possibilities of their children. It can be used to determine how likely you and
your spouse are to have children with freckles, their blood type, or the possibility of passing on a disease to them among other things.
Genetics Predictions To determine possible genotypes
of offspring, we use ______________________
Punnett squares -figures used to determine ___________________ ___________________________ based on the parents’ genotypes.
For example, if you crossed two heterozygous parents who have freckles, would their kids all have freckles, just some, or none at all?
Parent #2gametes
Parent #1gametes
How To Make a Punnett Square for a One-Factor Cross or Monohybrid Cross
Write the genotypes of the two organisms that will serve as parents in a cross.
In this example we will cross a male and female osprey that are heterozygous for large beaks.
They each have genotypes of Bb.
1 3
2 4
Practice
Trait: Number of fingersAlleles: F or f ____________: F codes for polydactyly so person has more than 5 fingers or toes.
_____________: f codes for normal five fingers or toes
Genotype Example Phenotype
Homozygous Dominant
FF
Homozygous Recessive
Five fingers
Heterozygous
Use a Punnett square to cross a normal parent with a heterozygous parent.
What are their chances of having a child with polydactyly?
Rules of Genetics
Early Ideas - Heredity►We know about genetics
because an Austrian monk named _______________ decided to run experiments on pea plants.
►Father of genetics►It was originally believed a
child’s traits were result of “blending” between parent’s traits
►Nothing was known about DNA!
Mendel’s Pea Plants
Why did Mendeluse pea plants?1. Peas ________________
___________________ ___________________ he could observe easily
2. He understood their method of reproduction3. They reproduced quickly
Characters investigated by Mendel
Reproduction in Plants
• Plant cells undergo meiosis, just like animals, to create plant gametes– Plant sperm =pollen – Plant egg = ovule
Reproduction in Plants• ____________
– Pollen released – Pollen fertilizes the
ovules– ____________________
___________. • Mendel could control
how plants were fertilized because he understood this process
• Pollination Animation
Genotype vs. Phenotype
►One trait Mendel followed through many crossed of peas was peas shape.
►Alleles:– ______________– ______________
Mendel’s Experiments
►____________________(P) “original” group mated
►________________(F1) offspring of the parental cross
►_________________(F2) offspring of crossing two F1 plants
Mendel’s First Experiment• Wanted to know what would
happen if cross 2 plants with different forms of a trait.
• The 1st thing Mendel did was cross 2 _____________ (homozygous) plants as the _______________________(P).
?
Results of the Cross?
►In F1 generation _____________resulted.
►What happened?►Round _____________ over wrinkled ►Do a Punnett square to show the
results he should have gotten.ALL ROUND F1
Principle of Dominance
►Round allele (R) dominated over wrinkled form of the gene (r)►Rule #1: .
one allele can dominate so trait coded by other allele hidden. – i.e. R dominates over r when both present– Because we know this, we
represent the round allele with a capital R.
Mendel’s 2nd Experiment
►Mendel extended his experiment and crossed two of his F1 plants…
►Do a Punnett square to show what results he should have gotten.
?
Results?
►After crossing two F1 plants, _________________, some F2 generation offspring showed recessive trait, some the dominant trait
►________(round: wrinkled)►25% wrinkled, 75% round►The wrinkle trait showed up
again.
Mendel’s Conclusions• - when gametes form, the two
copies of our genes are separated so each parent gives only one in their egg or sperm
• This gave us the idea of meiosis and how gametes are formed!
gametes
R or r
meiosis
R or rgametes
meiosis
Pea Parent 1: Pea Parent 2:RrRr
Mendels Conclusions cont.►Does everyone with brown hair have blue eyes?►Does everyone with freckles have a big nose? ►NO!►Mendel’s - inheritance of
one trait will not affect inheritance of another. Traits most of the time are not “_______” together!
►He saw pea plants with round peas and purple flowers, and pea plants with round peas and white flowers.
Mendel Video:
Independent Assortment
Mendel wondered if the _____________________ ______________another pair.
Mendel performed an experiment that followed two different genes as they passed from one generation to the next.
Because it involves two different genes, Mendel’s experiment is known as a _____________________. Single-gene crosses are ___________________.
The Two-Factor Cross: F1
Mendel crossed true-breeding plants that produced only round yellow peas with plants that produced wrinkled green peas.
The round yellow peas had the genotype RRYY, which is homozygous dominant.
The wrinkled green peas had the genotype rryy, which is homozygous recessive.
All of the F1 offspring produced round yellow peas. These results showed that the alleles for yellow and round peas are dominant over the alleles for green and wrinkled peas.
The Punnett square shows that the genotype of each F1 offspring was RrYy, ____________ ___________________________.
The Two-Factor Cross: F2
Mendel then crossed the F1 plants to produce F2 offspring.
Mendel observed that 315 of the F2 seeds were round and yellow, while another 32 seeds were wrinkled and green—the two parental phenotypes.
But 209 seeds had combinations of phenotypes, and therefore combinations of alleles, that were not found in either parent.
The alleles for seed shape segregated independently of those for seed color.
Genes that segregate independently—such as the genes for seed shape and seed color in pea plants—do not influence each other’s inheritance.
Mendel had discovered the principle of independent assortment.
______________________________________________________________________________________________________________________________________________________________________________________________________
Genetics Rules
►Rule #1: Dominance►Rule #2: dominance -some alleles aren’t
completely dominant so they BLEND ►Rule #3: -some alleles dominate
together so BOTH ARE SEEN►Rule #4: -ALL alleles on a male’s X
chromosome (X-linked) are expressed.
Complete Dominance
►Rule #1: Some alleles _________________ over others:– B= brown eyes– b=blue eyes– Bb= brown eyes, so B is
completely dominant.– One allele capital, the
other lower case
Incomplete Dominance
►Rule #2: Some alleles _______________________, so they ____________:– R= red flowers– R = white flowers– Rr = pink flowers– One allele capital, the other
lower case
PINK FLOWERS!!! BLENDING!!!
Codominance►Rule #3: Some alleles __________________ so they
BOTH are shown– H = brown hair on horses– H’ = white hair on horses– HH’ = both brown and white hairs, so the horse is roan
color.– Blood types are like this, too.
Antigens-markers on cells
Blood type determined by your markers on your red blood cells
4 blood group phenotypes:Type A has A antigens
Type B has B antigens
Type AB has A and B antigens
Type O has no antigens
Blood Types
Multiple Alleles
Multiple alleles- 3 different forms of the gene code for blood types IA, IB, and i– Allele IA codes for “A”
antigen – IB codes for “B” antigen– i codes for none
Multiple Alleles
• 6 blood group genotypes• ___________________-
IA and IB dominate over i• ____________- IAIB
genotype shows BOTH A and B antigens
• Both alleles that codominate are written with capital letters!
Blood Types►Your body’s immune systems creates antibodies
against anything foreign– Antibodies-proteins produced by your immune system
to fight off things that look “foreign.”►Type A--makes anti-B antibodies►Type B--makes anti-A antibodies►Type AB--makes NO antibodies— universal receiver►Type O--makes anti-A and anti-B antibodies—
universal donor
Sex-Linked Genes
►Rule #4: sex-linked genes: ALL alleles on a male’s X chromosome (X-linked) are expressed.– Male sex chromosomes?
_________– Female sex chromosomes?
_________– We also call sex-linked genes by
another name, X-linked, because the X chromosome has the majority of the genes.
Sex-Linked Genes
► In males, EVERY gene on their X chromosome is expressed. The Y doesn’t have the same genes.
► In females this is not the case because they have another copy on their other X chromosome to overcome it.
Genes: _____ _____ _____ ___
Sex-Linked Genes
►Examples of sex-linked disorders:– Colorblindness
– Hemophilia– Fragile X Syndrome– Duchene Muscular Dystrophy – Cleft Palate– Vitamin D Resistant Ricketts– 3 types of deafness– Male Pattern Baldness
X-linked recessive disorder
Sex-Linked Genes►Genes that occur on sex
chromosomes are written with X’s and Y’s to show this special situation.– I.e. red-green colorblindness is a
recessive trait. It is found on the X chromosome, not the Y.
– We write the alleles this way:►X¢ = colorblindness►XC = normalThe slash indicates it is a lower case
letter so there is no confusion
Sex-Linked Genes
►Try to complete this table:
PhenotypesPhenotypes GenotypesGenotypes
Normal MaleNormal Male
Colorblind MaleColorblind Male
Normal FemaleNormal Female
Normal Normal ““carriercarrier”” FemaleFemale
Colorblind femaleColorblind female
What is a Karyotype? Karyotype- __________
____________________ in a somatic cell.
46 chromosomes in a normal, human karyotype 23 pairs of
homologous chromosomes – pairs of chromosomes with similar structure and function
Amniocentesis Method for obtaining fetal cells
from fluid surrounding fetus. Chromosomes can be obtained
from these cells for a karyotype.
This is a “risky” procedure. Should ONLY be performed on
women who:a) Are in their mid 30’s or older.b) Have had a previous child
with a chromosomal defect.
What can be determined from looking at a
karyotype?
_____________________ Autosomes-all
chromosomes except sex chromosomes
Sex chromosomes -either XX (female) or XY (male)
_____________________
Two Types of Mutations Gene mutation- ___________________________________ Chromosomal mutation- ____________________________
__________________________________________ Either type of mutation can involve autosomes
(chromosomes 1-22) or sex chromosomes (X & Y)
Gene Mutations Gene mutation- single gene
defective _____________ _____________ _____________
Insertion
Deletion
Subtitution
Chromosomal Mutations
Chromosomal mutation- missing or extra entire chromosome and ALL its genes ___________—having one less chromosome
(45) ___________—having an extra chromosome
(47) ___________—missing part of a chromosome
Autosomal Disorders _________________- disease involving the 22
pairs of chromosomes that are NOT sex chromosomes (X,Y) and any genes on them.
Can result from Gene mutation: defective gene
on autosome Chromosomal mutation: loss
or gain of autosome
Aa
Aa Aa
aaAaAA
Autosomal DisordersGene Mutations
1- Cystic Fibrosis Recessive disorder Mutated gene on chromosome
17. Characterized by excessive,
THICK secretion of the mucus in the body.
Autosomal DisordersChromosomal Mutations
Down Syndrome 1 in 1,000 live births. Trisomy-extra
Chromosome 21 Risk increases with mom’s
age Mild to severe mental
retardation
Sex-Linked Disorders Sex-linked disorder – _________________________________
__________________________________________________. Recessive gene on the X chromosome is ____________
to be expressed in males ***Y chromosome has no 2nd allele that might
counteract the gene on the X chromosome!
Sex-Linked DisordersGene Mutations
1- Color Blindness X-linked recessive disorder Gene mutation on X
chromosome 1 of 10 males
2- Hemophilia X-linked recessive disorder Gene mutation on X
chromosome. 1 of 5,000 males Interfere with normal blood
clotting
ONLY THE SEX CHROMOSOMESARE INVOLVED
Sex-Linked DisordersChromosomal Mutations
1- Klinefelter Syndrome (XXY) 1 of 1,000 males. Trisomy- extra X chromosome
Sex-linked DisordersChromosomal Mutations
2- Turner’s Syndrome (XO) 1 of 10,000 females Monosomy- one of X chromosomes
is either missing or inactive Have immature female appearance
and lack internal reproductive organs.
GENETIC DISORDERS
________________Chromosomes 1-22
_____________________Sex Chromosomes X and Y
Gene Mutations_______________ ______________________________
ChromosomalMutations
______________________________________
_______________1 gene mutated
on X chromosome
______________________________
Extra or missing Sex chromosome
EXAMPLES?
How Do We Know About Our Genes?
Human Genome Project Began in 1990; complete 2003
Goals: Determine complete sequence of the 3
billion DNA bases in human DNA Identify all human genes for further
biological study
The Unknown
________________, exact locations and functions Gene ______________ _______________ organization Chromosomal structure and organization
Ethical, Legal and Social Issues
Fears Genetic information used to harm or
discriminate Deny access to health insurance Deny employment Deny education Deny loans? Cloning?
DNA Databases
Cloning
_____________ -creating many genetically identical cellsfrom one cell.
Creation of genetically identical organisms
Why Clone Animals?
To answer questions of basic BiologyFive genetically identical cloned pigs.
For herd improvement.
To satisfy our desires (i.e. pet cloning)
For pharmaceutical production.
Is Animal Cloning Ethical?
The first cloned horse and her surrogate mother/genetic twin.
As with many important questions, the answer is beyond the scope of science.
Biotechnology
Dolly and surrogate
Mom
Genetically modified rice.Embryonic stem cells and gene therapy