Genetics

Question 1

Define genotype.

Answer 1

Genetic constitution of an organism.

Question 2

Define phenotype.

Answer 2

The expression of the genetic constitution of an organism and its interaction with the environment.

Question 3

Define homozygous.

Answer 3

A pair of homologous chromosomes carrying the same allele for a single gene.

Question 4

Define heterozygous.

Answer 4

A pair of homologous chromosomes carrying different alleles for a single gene.

Question 5

Define recessive allele.

Answer 5

Allele only expressed if there are no dominant alleles.

Question 6

Define dominant allele.

Answer 6

Allele that will always be expressed if present.

Question 7

Define codominant.

Answer 7

Both alleles are equally dominant and expressed in phenotype.

Question 8

Define multiple alleles.

Answer 8

More than two alleles for a single gene.

Question 9

Define sex-linkage.

Answer 9

A gene whose locus is on the X chromosome

Question 10

Define autosomal linkage.

Answer 10

Genes that are located on the same chromosome (NOT sex chromosomes)

Question 11

Define epistasis.

Answer 11

When one gene modifies/masks the expression of a different gene at a different locus.

Question 12

Define monohybrid.

Answer 12

Genetic inheritance cross of characteristics determined by one gene.

Question 13

Define dihybrid.

Answer 13

Genetic inheritance cross of characteristics by two genes.

Question 14

What is the genetic coding of a monohybrid? Give an example.

Answer 14

single letter.
i.e. B or b

Question 15

What is the genetic coding of a codominant allele? Give an example.

Answer 15

Gene^allele.
I^A or I^B

Question 16

What is the genetic coding of multiple alleles? Give an example.

Answer 16

Gene^allele.
I^A I^B

Question 17

What is the genetic coding of sex-linkage? Give an example.

Answer 17

Chromosome^allele
X^B or X^b

Question 18

What is the genetic coding of a autosomal linkage? Give an example.

Answer 18

single letter.
AaBb

Question 19

What is the genetic coding of epistasis? Give an example.

Answer 19

single letter.
EeBb

Question 20

What is the process of creating a dihybrid cross?

Answer 20

1. Parental phenotype
   i.e. Round, yellow and green, wrinkled
2. Parental genotype:
   i.e. RRYY and rryy
3. Possible gametes:
   i.e. 4x RY or 4x ry
4. Offspring genotype:
   i.e. RrYy
5. Possible offspring phenotype:
   i.e. Round, yellow
6. Proportion of each phenotype:
   i.e. 100%

Question 21

How does crossing over in meiosis affect genetics?

Answer 21

Results in new combinations of alleles so predicted gametes in punnet square may differ.

Question 22

How does autosomal linkage affect genetics?

Answer 22

The dominant allele for each gene linked on the same chromosome will be inherited together.

Question 23

How does autosomal linkage affect the predicted phenotype ratios?

Answer 23

A & B are linked and a & b are linked.
New possible gametes: AB or ab.
Instead of w/out: AB, Ab, aB, ab

Question 24

How does autosomal linkage and crossing over together affect genetics?

Answer 24

Because of AL, you would expect two phenotypes. But if you also experience crossing over, then you can observe more than two phenotypes.

Question 25

What is crossing over in meiosis in terms of genetics?

Answer 25

1. Homologous pair of chromosomes after DNA replication (interphase)
2. Chromatids cross over during meiosis
3. New combinations of alleles

Question 26

What is Chi-squared test?

Answer 26

Statistic to investigate differences between frequencies.

Question 27

Why do we use Chi-squared?

Answer 27

To determine whether there is a significant difference between the expected frequency and the observed frequency.

Question 28

What does the null hypothesis state?

Answer 28

There is no significant difference between the expected frequency and the observed frequency.

Question 29

What are the headings for the Chi-squared table?

Answer 29

Category, observed, expected ratio, expected, (O-E), (O-E)^2, (O-E)^2/E

Question 30

What is the equation of Chi-squared?

Answer 30

X^2 = sum of (O-E)^2/E

X^2 is Chi-squared
O is observed frequency
E is expected frequency

Question 31

How would you calculate degrees of freedom?

Answer 31

Number of categories - 1

Question 32

What is the probability of the table usually?

Answer 32

P = 0.05

Question 33

How would you determine whether to accept or reject null hypothesis?

Answer 33

X^2 < critical value then accept null
X^2 > or = critical value then reject null