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UNDERSTANDING HEREDITY

GENETICS AND MUTATIONS

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GeneticsPart One

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Genetics is…OThe scientific study of heredity

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A gene is…OA sequence of DNA that codes for a protein and determines traits

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What is an allele?OOne of two or more alternative forms of a gene that are found at the same place on a chromosome.

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What does the term heterozygous mean?

OThe organism has two different alleles for a trait.

OExample: Tt Bb

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What does the term homozygous mean?

OThe organism has two of the same alleles for a trait.

OExample: TT or tt BB or bb

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OComplete section determining heterozygous or homozygous genotypes

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What is a genotype?OThe actual genetic makeup of an organism.

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What is a phenotype?OThe physical characteristics of an organism.

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OComplete section on phenotype/genotype

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Who was Gregor Mendel?

OThe “Father” of genetics

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What was his contribution?

OHis experiments laid the foundation of the science of genetics.

OHe noticed that traits could disappear in one generation and reappear in later generations.

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Gregol MendelBorn July 20, 1822

Heinzendorf bei Odrau, Austrian Empire (now Hynčice, Czech Republic)

Died January 6, 1884 (aged 61)Brno (Brünn), Austria-Hungary (now Czech

Republic)Nationality Empire of Austria-Hungary

Fields GeneticsInstitutions St Thomas's Abbey

Alma mater University of OlomoucUniversity of Vienna

Known for Creating the science of genetics

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OComplete section on monohybrid crosses

ONow start “Practice with Crosses”

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GeneticsPart Two

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Define Independent Assortment

OIndependent segregation of genes during the formation of gametes.

ORemember: Meiosis is the formation of gametes.

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Define Law of Segregation

OSeparation of alleles during gamete formation.

OExample: 1 of 2 alleles for eye color will go to each sperm or egg

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Define Co-dominantOBoth alleles of a gene contribute to the phenotype

OExamples: Type AB blood; 1 blue eye and one green eye; speckled chickens

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Define Incomplete Dominance

OOne allele cannot dominate another; the final phenotype is a blend of the 2 alleles

OExample: cross a red carnation with a white carnation makes a pink carnation

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Co-dominance Incomplete Dominance

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ORedefine genotype and phenotype

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Co-DominanceHow many

genotypes are there?

How many phenotypes are

there?

OThree: AA,BB, AB

OThree

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OComplete examples of incomplete dominance.

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Incomplete dominanceHow many

genotypes are there?

How many phenotypes are

there?

OThree: RR-red rr-white Rr-pink

OThree

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OComplete examples of co-dominance.

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GeneticsPart Three

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Sex chromosomesWhat are the female sex

chromosomes?What are the male sex chromosomes?

OXX OXY

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What does it mean for a trait to be sex-linked?

OIt is carried on one of the sex chromosomes, most likely the X

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Examples of sex-linked traits would be…

OThe ability to see color (color blindness)

OHaving a full head of hair (baldness)

OBlood clotting properly (hemophilia)

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What is a di-hybrid cross?

OA cross between two individuals with two different traits that you are studying

OComplete examples and problems

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Mutations

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What is a mutation?OGenes code for…

OMutations are…

OProteins

OMistakes in genetic code that affect the final protein

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What is a point mutation?

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A mistake in one nitrogen base of an

mRNA codon

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Types of point mutations:

O Substitution – 1 nucleotide is switched for another

Example: CAT GCA CAT GCGO Insertion or deletion – 1 nucleotide is

inserted/deleted in sequence Example: CAT GCA CAT GAC A Example: CAT GCA CAT CA

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Effects of point mutations

O Substitution

O Insertions/deletions

O Might have no effect on/or will only effect one amino acid

O Change how the sequence is read – called a frameshift mutation

38epidermolysis bullosa 

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What is a chromosomal

mutation?

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A change in the number or structure of

chromosomes.

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Types of chromosomal mutations

ODeletion - entire gene(s) deleted

ODuplication – an extra copy of gene(s) added

O Inversion – segment of chromosome is flipped over and reversed in place

OTranslocation – segment of chromosome breaks off/relocates to another

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Can be the result of:Inversion, deletion or translocation

Result of:Duplication

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When mutations go…Wrong Right

ODisruption of biological activities

ODisabilityODeath

OSource of genetic variation

OMay allow some members of a species a better chance to survive

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