GENETICSBiology

Chapter 10-12

Gregor Mendel- the Father of GeneticsAustrian monkworked in gardens in monastery

studied pea plants

studied heredity- passing on of traits or characteristics from parents to offspring

genetics – the branch of biology that studies heredity

traits- characteristics that are inherited

gametes- sex cells; sperm and egg cells

fertilization- when sperm unites with egg cell forming a 1 celled structure called a zygote

in plants, achieved thru pollination

2 types of reproduction:1. Asexual reproduction- when there is

NO exchange of genetic information between organismsex: mitosis in paramecium

2. sexual reproduction- where there is an exchange of genetic info between orgex: meiosis

in unicellular organisms, MITOSIS is form of asexual reproductionwon’t go thru MEIOSIS

in multicellular organisms, (plants, animals, us, etc) MITOSIS is how more cells are formedMEIOSIS is how sperm & egg cells

are formed

on chromosomes, there are segments that code for specific traits; segments are called GENES

genes are the factors that offspring have received from mom & dad

chromatid

SISTER CHROMATIDS

chromosome

child receives one chromosome from mom and one fromdad for each DNAmolecule in species

genes code for traitstraits are characteristics

that are inherited alleles- alternate forms

of genes

receive 1 allele from mom & 1 allele from dad for each trait

represent alleles by using LETTERS

dominant allele is represented by a CAPITAL LETTER

represents the trait that is stronger or dominant

(usually will use the 1st letter of the dominant trait)

for ex: rolling tongue is a dominant trait in humans

usually use R to represent ability to roll tongue

recessive alleles are represented by a small letter

represents the weaker or hidden trait

for example, not being able to roll your tongue is a recessive trait

represented by r

terms we have to learn:

phenotype- physical appearance of the trait in the organism

genotype- gene or allele combination of an organism for that traitex: RR or Rr or rr

got 1 from mom; 1 from daduse the combo of letters to represent genotype

more terms to learn: homozygous dominant-

means 2 capital letters (dominant trait)

homo= same aka: pure dominant for ex: RR= can roll tongue

homozygous recessive- 2 little letters ( 2 recessive alleles)

aka: pure recessive for ex: rr = can’t roll tongue

heterozygous- have 1 capital letter (dominant trait) & 1 little letter (recessive trait)

hetero= different (means size here or trait)

aka: hybrid

for ex: Rr What does this genotype mean?

can roll tongue Why?

Dominant: L k e M r O d S E Recessive: Mp Q t r D K n s Homozygous Dominant: BB Hh gg TT Rr Homozygous Recessive: ff Aa Cc tt KK Ll mm

Offspring combinations in which dominant trait must show:BB Dd ee Jj Rr ii

Offspring combinations in which recessive phenotype must show:Ee ff Hh ii Ll nn Oo

Dominant: L k e M r O d S E Recessive: M p Q t r D K n

s Homozygous Dominant: BB Hh gg TT Rr Homozygous Recessive: ff Aa Cc tt KK Ll mm

Offspring combinations in which dominant trait must show:BB Dd ee Jj Rr ii

Offspring combinations in which recessive phenotype must show:Ee ff Hh ii Ll nn Oo

to figure out traits organisms inherit:

use a Punnett square perform monohybrid crosses use a 4 box square

Karotype

Meiosis in multicellular org, there are 2 types of

cells:1. body cells (somatic) stomach, bone,

nervous, etc2. sex cells (gametes)- sperm, egg

inside somatic cells, you’ll find 2 of each kind of chromosome= DIPLOID (2n)

inside sex cells, you’ll find only 1 of each kind of chromosome= HAPLOID (n)

chromosomes occur in pairs called homologous chromosomeshave genes for the same traits located in the same positions

they are not genetically identical (we got 1 from mom, 1 from dad)

we have 23 pairs of these homologous chromosomes

somatic cells (body) have 46 chromosomes in them

in sex cells (sperm or egg) we have just 23 chromosomesthis is IMPORTANT WHY?

different organisms have different numbers of chromosomes in their cells

look p. 265

chromosome # does NOT indicate complexity

if an org has 24 chromosomes in its body cells, how many chromosomes will be in the sex cells?

What would happen in humans if the sperm and egg cells each contained 46 chromosomes?

the resulting zygote would have 92

SOMETHING has to occur to prevent too many chromosomes

Meiosis- process of nuclear division that reduces chromosome # by half

meiosis is involved in sexual reproduction

results in haploid cells – makes sperm & egg cells

in order to happen, there has to be 2 nuclear divisions

similar to mitosis, but divides twice

divided into Meiosis I & Meiosis IIsame names as mitosis (easier)

Interphase-chromosomes are replicated, but aren’t visible yet

Prophase I chromosomes

become visible nucleus/ nucleolus

disapppears UNIQUE to meiosis:

homologous chromosomes form TETRAD

chromatids are paired tightly; genetic material is exchanged= CROSSING OVER

Metaphase I tetrads line

up at equator (middle)

UNIQUE:homo chromos are lined up as PAIRS

Anaphase I homo chromos

separate & move to opposite ends of cell

UNIQUE: centromeres do NOT split- this ensures that each new cell only receives ONE chromosome from each parent

Telophase I spindles break down

chromosomes uncoil cytoplasm divides to 2

cells each new cell has ½

genetic info of parent cell

another division must occur because chromosomes were copied

Prophase II new spindle

fibers form chromosom

es are visible again

Metaphase II chromosom

es line up individually at middle of cell

Anaphase II centromeres

split sister

chromatids separate & move to opposite ends of cell

Telophase II

spindles break down

nuclei reforms

cytoplasm divides

Results of meiosis 4 haploid cells formed from

original diploid cell

they become gametes- sperm and egg cells