U3: C14: Genetics

Question 1

1st law of segregation (mendel)

Answer 1

1. Genes exist in alter. forms (alleles)
2. 2 alleles per gene, 1 from each parent (diploid = 2n = 46 chrmomsomes = 26 chromosome pairs)
3. 2 alleles segregate during meiosis to make haploid (n = 26 chromosomes) gametes
4. Dominate and recessive expression 3:1 phenotype

***Which allele goes into which gamete.. Random

http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/13295802/andrews_figure1_ksm.jpg

Question 2

2nd law of independent assortment (mendel)

Answer 2

each gene inheritanfe is independent of the inheritance of other genes.

• GENE IS UNLINKED
• TtPp x TtPp 9:3:3:1 phenotype

(if gene is linked will not follow this law)

Question 3

Hetrozygous Mitosis vs Meiosis

Answer 3

1. Mitosis

AA aa -anaphase-> (<-A & <-a a-> & A->) sister chromatid sperated

• telophase-> x2 (A a)
  2. Meiosis

AA aa tetrad -anaphase 1-> (<-AA aa->) Homolog chromosome seperate

-telophase 1-> (AA) & (aa) , will then go through Meiosis 2 which is identical to Mitosis 1 and result in a haploid

http://3219a2.medialib.glogster.com/media/9a/9a3b9f2634af6ecc76a2c46c9aee5e62b1d862a4a5ca774eb43a4eced83a03c5/mitosis-vs-meiosis-1-jpg.jpg

Question 4

Independent Assortment occurs during when? And what is the function?

Segregation purpose?

Answer 4

1. Meiosis I, reduction division
2. both independent assortment and segregation is ment to increase genetic diversity

Question 5

Genetic Linkage

Answer 5

NON INDEPENDENT ASSORTMENT!

-not follow 9:3:3:1 or 3:1 phenotypic ratio

Frequency of recombination can tell you if it linked or not. (0% = linked, 50% unlinked)

Question 6

Frequency of Recombination

a. linked
b. unlinked

Answer 6

a. 0% (linked follows independent assortment, therefore 9:3:3:1 and 3:1 phenotype)

AB*AB ab*ab -> (AB) (AB) (ab) (ab) = 0% recombinate

b. 50% (unlinked, crossing over occurs during Prophase I when tetrads line up)

AB*AB ab*ab -crossing over-> AB*Ab aB*ab -> (AB) (Ab) (aB) (ab) = **50% recombinate, **50% not recombinate

Question 7

Genetic mapping

Answer 7

Close the 2 genes are, more likely they will be linked and there will be no crossing over (no recombination).

Farther the 2 genes are, more likely they will be crossing over between them and recombination will occur.

• You can use recombinate frequency to approximate location of the genes.
• 1 map unit = 1% chance of recombination

Question 8

Recombination Frequencies

AB 6%

BC 18%

AD 5%

CD 17%

AC 12%

BD 1%

Answer 8

B-1-D-5-A-12-C

BDAC

Question 9

Variations on Mendelian Genetics

Name the 4 types

Answer 9

1. incomplete Dominance
2. codominance
3. penetrance
4. expressivity

Question 10

Incomplete Dominance

Answer 10

1:2:1 phenotype, Heterozygous is an intermediate of the parent

Question 11

Codominance

Answer 11

multiple alleles with at least 2 alleles dominate to a third. (ABO) (AB = I^AI^{<span>B</span>}) or (AO = I^{<span>A</span>}i)

Question 12

Penetrance

Answer 12

geneotype # of individuals in a population carryingthe alleles who activiely express the phenotype

Question 13

Expressivity

Answer 13

varying expression of disease symntpons despite identical genotype

Question 14

Autosomal vs Sex Chromosomes

Answer 14

autosomal= all chromsomes that exclude the sex chromosomes

sex chromosomes= Men XY, Females XX

Aneuploidy = worse in autosomal chromosomes compared to sex chromosomes

Question 15

Aneuploidy

Answer 15

abnormal number of chromosomes, any variation from 46 (2n) in autosomal chromosome.

Usually caused by nondisjunction either in Meiosis I or II

Trisomy (2N + 1)

Monosomy (2N - 1)

Question 16

pleiotropic

Answer 16

multiple phenotypic effects

Question 17

epistasis

Answer 17

gene at one locus alters phenotypic expression at another gene at a 2nd locus