GeneticsGeneticsGeorgia High School Georgia High School

Graduation Test: Science Graduation Test: Science ReviewReview

IntroductionIntroduction•From the key vocabulary, From the key vocabulary,

circle the words that you can circle the words that you can already define or use in a already define or use in a sentence.sentence.

•Write down two or three things Write down two or three things that you think are important that you think are important for you to know today.for you to know today.

GeneticsGenetics

•The study of the The study of the inheritance of traits and inheritance of traits and how genes pass on these how genes pass on these traits from parents to traits from parents to offspringoffspring

Important Genetic Important Genetic VocabularyVocabulary

• traittrait: a characteristic of an : a characteristic of an organism that is inherited organism that is inherited (examples: eye color, hair type, (examples: eye color, hair type, etc.) etc.)

•genegene: basic unit of heredity : basic unit of heredity made of DNA that determines made of DNA that determines the characteristics of a traitthe characteristics of a trait

•alleleallele: the two different versions : the two different versions of a gene for a particular trait of a gene for a particular trait (one received from each parent)(one received from each parent)

Genotype versus Genotype versus PhenotypePhenotype

GENOTYPEGENOTYPE• an organism’s an organism’s

genetic makeupgenetic makeup• includes the two includes the two

allelesalleles• represented represented

with two letters with two letters (example: Bb) (example: Bb)

PHENOTYPEPHENOTYPE• the physical the physical

appearance of a appearance of a traittrait

• expressed by the expressed by the organisms genesorganisms genes

• represented by represented by description description (example: brown (example: brown eyes)eyes)

Dominant versus Dominant versus RecessiveRecessive

DOMINANTDOMINANT• an allele that an allele that

expresses itself expresses itself while hiding the while hiding the effects of another effects of another alleleallele

• represented with a represented with a capital lettercapital letter

• example: Bb example: Bb (dominant brown (dominant brown eyes dominates over eyes dominates over recessive blue)recessive blue)

RECESSIVERECESSIVE• An allele whose An allele whose

effects are hidden effects are hidden by a dominant alleleby a dominant allele

• Represented with a Represented with a lower-case letterlower-case letter

• example: Bb example: Bb (dominant brown (dominant brown eyes dominates eyes dominates over recessive blue)over recessive blue)

Homozygous versus Homozygous versus HeterozygousHeterozygous

HOMOZYGOUSHOMOZYGOUS• ““homo-” means homo-” means

the samethe same• the pairing of the pairing of

alleles that are the alleles that are the samesame

• examples: examples: • BB is dominant BB is dominant

homozygous brown homozygous brown • bb is recessive bb is recessive

homozygous bluehomozygous blue

HETEROZYGOUSHETEROZYGOUS• ““hetero-” means hetero-” means

differentdifferent• the pairing of the pairing of

unlike allelesunlike alleles• example:example:

• Bb is Bb is heterozygous heterozygous brownbrown

Sample QuestionSample Question

1.1.Explain how traits are Explain how traits are passed from generation passed from generation to generation.to generation.

Gregor MendelGregor Mendel

•Father of GeneticsFather of Genetics•experimented with pea experimented with pea plantsplants

•established a method for established a method for predicting how traits are predicting how traits are inheritedinherited

Mendel’s LawsMendel’s Laws• The Law of DominanceThe Law of Dominance: a recessive trait : a recessive trait

will only be expressed when the organism’s will only be expressed when the organism’s genotype is recessive homozygous (bb)genotype is recessive homozygous (bb)

• The Law of SegregationThe Law of Segregation: during : during fertilization, new alleles are randomly fertilization, new alleles are randomly formed; one can only predict offspring formed; one can only predict offspring (using Punnett squares)(using Punnett squares)

• The Law of Independent AssortmentThe Law of Independent Assortment: : each trait is inherited independently of each trait is inherited independently of other traits other traits

Probability and Punnett Probability and Punnett SquaresSquares

• Probability is the likelihood an event will occurProbability is the likelihood an event will occur• Geneticists use Punnett squares to predict the Geneticists use Punnett squares to predict the

probability of genetic combinationsprobability of genetic combinations• Example: When two heterozygous brown eyes Example: When two heterozygous brown eyes

mate . . . mate . . .

BB bb

BB BBBB BbBb

bb BbBb bbbb

Theory of Theory of InheritanceInheritance• Chromosomes are the physical basis Chromosomes are the physical basis

of inheritance (carry DNA).of inheritance (carry DNA).• Variability results from dominant and Variability results from dominant and

recessive alleles.recessive alleles.• The chromosomes in the male gamete The chromosomes in the male gamete

and female gamete join together and female gamete join together during fertilization to form a zygote.during fertilization to form a zygote.

•gamete = sex cellgamete = sex cell•zygote = fertilized eggzygote = fertilized egg

Sample QuestionSample Question

2.2.Explain the role of DNA Explain the role of DNA and RNA in heredity.and RNA in heredity.

DNADNA•deoxyribonucleic aciddeoxyribonucleic acid• found in chromosomes in the found in chromosomes in the

nucleusnucleus•determines the hereditary traits of determines the hereditary traits of

an organisman organism•contains all the information contains all the information

needed for the production of needed for the production of proteinsproteins

•protein sequences determine traitsprotein sequences determine traits

RNARNA• ribose nucleic acidribose nucleic acid• aids in protein synthesis in the ribosomeaids in protein synthesis in the ribosome• 3 types:3 types:

•messenger RNAmessenger RNA: mRNA carries the DNA : mRNA carries the DNA nucleotide sequence for a protein from the nucleotide sequence for a protein from the nucleus to the ribosomenucleus to the ribosome

•transfer RNAtransfer RNA: tRNA transports amino acids : tRNA transports amino acids (building blocks of proteins) to the ribosome(building blocks of proteins) to the ribosome

•ribosomal RNAribosomal RNA: rRNA makes up the : rRNA makes up the structure of the ribosomestructure of the ribosome

Sample QuestionSample Question

3.3.Diagram and explain Diagram and explain DNA replication.DNA replication.

DNA replicationDNA replication• self-duplication of the genetic materialself-duplication of the genetic material• results in two new DNA moleculesresults in two new DNA molecules• occurs during interphase (just before occurs during interphase (just before

cell divides)cell divides)• proteins unwind the DNA helix and each proteins unwind the DNA helix and each

strand acts as a template for a new strand acts as a template for a new strandstrand

• unbound nucleotides attach . . . unbound nucleotides attach . . . • A-T (adenine binds with thymine)A-T (adenine binds with thymine)• C-G (cytosine binds with guanine)C-G (cytosine binds with guanine)

Sample QuestionSample Question

4.4.Diagram and explain Diagram and explain transcription.transcription.

DNA transcriptionDNA transcription• to “transcribe” is to copyto “transcribe” is to copy• mRNA is synthesized in the cell nucleus mRNA is synthesized in the cell nucleus

from the DNA moleculefrom the DNA molecule• Just as in replication, the helix unwinds Just as in replication, the helix unwinds

and free nucleotides attach to make and free nucleotides attach to make mRNA. . . mRNA. . .

• C-G (cytosine binds with guanine)C-G (cytosine binds with guanine)• U-A (uracil binds with adenine)U-A (uracil binds with adenine)• Only DNA has thymineOnly DNA has thymine

• mRNA separates and moves out of the mRNA separates and moves out of the nucleusnucleus

• DNA double helix reformsDNA double helix reforms

Sample QuestionSample Question

5.5.Diagram and explain Diagram and explain translation.translation.

DNA translationDNA translation

•process of translating the process of translating the genetic code to the genetic code to the amino acid sequenceamino acid sequence

•tRNA decodes the mRNA tRNA decodes the mRNA to read the DNA in order to read the DNA in order to make the correct to make the correct proteinprotein

MutationsMutations•A mutation is any change in A mutation is any change in

the DNA sequence.the DNA sequence.•A change in one nucleotide A change in one nucleotide

may cause a change in the may cause a change in the structure of the protein.structure of the protein.

•During pregnancy, observing During pregnancy, observing a karyotype (a chromosome a karyotype (a chromosome picture) can detect picture) can detect chromosomal defects.chromosomal defects.

DiscussionDiscussion•If you needed to get precise If you needed to get precise

information from one person information from one person to another, what would you to another, what would you need to do? How would you need to do? How would you structure the information? structure the information? How would you store that How would you store that information so that it could information so that it could be easily retrieved?be easily retrieved?

Lesson SummarizedLesson Summarized

•Write a sentence that Write a sentence that explains the system explains the system discussed.discussed.

•Draw a graphic organizer Draw a graphic organizer that shows the relationship that shows the relationship of the parts of the gene of the parts of the gene system to the whole system.system to the whole system.