Genetics

Question 1

Define gene

Answer 1

Seq. of bases on DNA that codes for protein

Question 2

Define allele

Answer 2

Diff. version of a gene

Question 3

Define genotype

Answer 3

Genetic makeup of an organism

Question 4

Define phenotype

Answer 4

Expression of genotype + it’s interactions w/ the env

Question 5

Define dominant

Answer 5

Allele whose characteristic appears in phenotype even when there’s only 1 copy

Question 6

Define recessive

Answer 6

Allele whose characteristics appear if 2 copies are present

Question 7

Define codominant

Answer 7

Alleles both expressed in the phenotype

Question 8

Define locus

Answer 8

Fixed position of a gene on c’some

Question 9

Define homozygote

Answer 9

Organism that carries same allele

Question 10

Define heterozygote

Answer 10

Organism that carries 2 diff alleles

Question 11

Define carrier

Answer 11

Person carrying allele which is not expressed in phenotype but can be passed onto offspring

Question 12

Humans are diploid organisms. What does this term mean?

Answer 12

2 alleles for each gene

Question 13

What is the phenotypic ratio in a monohybrid btw homo dom + homo rec? (RR x rr)

Answer 13

3:1

Dominant : Recessive

Question 14

What is the phenotypic ratio in a dihybrid btw hetro? (RrYy x RrYy)

Answer 14

9 : 3 : 3 : 1

Dom : Hetro : Hetro : Rec

Question 15

When are characteristics described as sex-linked?

Answer 15

Allele that codes for characteristic is located on sex c’some

Question 16

What are the sex c’somes in females?

Answer 16

XX

Question 17

What are the sex c’somes in males?

Answer 17

XY

Question 18

Outline a diff. btw Y c’somes and X c’somes

Answer 18

Y is smaller so carriers fewer genes

Question 19

Why are males more likely to show recessive phenotype for sex-linked genes?

Answer 19

Males only have one X c’some, often have 1 allele so express characteristic even if recessive

Question 20

Define autosome

Answer 20

C’somes that aren’t sex c’somes

Question 21

Why are genes on the same autosome said to be linked?

Answer 21

Same autosome stay together during independent segregation + passed onto offspring

Question 22

When are autosomes not linked?

Answer 22

When crossing over occurs

Question 23

When are autosomal genes said to be more closely linked?

Answer 23

Closer together two genes are on autosome bc crossing over is less likely to split them up

Question 24

Define epistatis

Answer 24

Allele of one gene masks the expression of the alleles on the other genes

Question 25

What is the chi-squared test used for?

Answer 25

Test to compare the goodness of fit of observed + expected results

Question 26

Chi-squared value is larger than or equal to critical value

Answer 26

• Significant diff.
• Less than 5% probability diff. due to chance
• Reject null

Question 27

Chi-squared value is smaller than or equal to critical value

Answer 27

• No significant diff.
• More than 5% probability diff. due to chance
• Accept null

Question 28

How do you work out the chi-squared value?

Answer 28

(O-E)² / E

• O = observed
• E = expected

Question 29

After working out the chi-squared value, what do you do?

Answer 29

• Degrees of freedom - no. classes minues 1
• Critical value at probability of 0.05
• Compare critical w/ chi-squared value