WEEK 8 - Mendelian inheritance

Question 1

What is a point mutation?

Answer 1

A single-base substitution in the DNA sequence.

Examples include changes in the sequence such as TGCATTCG to TGCATTCG.

Question 2

What is an insertion mutation?

Answer 2

A sequence of DNA (any length) inserted into existing DNA.

Example: TGCATTCG to TGCATTTAGGC.

Question 3

What is a deletion mutation?

Answer 3

A sequence of DNA (any length) removed from existing DNA.

Example: TGCATTCG to TGCATTCCG.

Question 4

What occurs during gene duplication?

Answer 4

Any number of genes can be duplicated, potentially even entire genomes.

Question 5

Define inversion in genetics.

Answer 5

A segment of DNA is flipped around and re-inserted.

Question 6

What is chromosome fusion?

Answer 6

When two chromosomes become joined together as one.

Question 7

What do mutations generate?

Answer 7

Genetic diversity.

Question 8

What is a genotype?

Answer 8

The genetic composition of an organism.

Question 9

What is a phenotype?

Answer 9

The physical manifestation of the genotype.

Question 10

True or False: Mendel’s experiments showed that inheritance is blending.

Answer 10

False.

Mendel’s work suggested that inheritance is particulate, not blending.

Question 11

What is the ratio of gametes produced by two heterozygous parents for a single gene?

Answer 11

1:2:1.

Question 12

What is a polygenic trait?

Answer 12

A trait influenced by many genetic loci.

Question 13

Define quantitive genetics.

Answer 13

The study of the genetic mechanisms of continuous phenotypic traits.

Question 14

What is broad sense heritability?

Answer 14

Proportion of phenotypic variance explained by genetic differences among individuals.

Question 15

Fill in the blank: The equation for heritability is h2 = _____ / VP.

Answer 15

VG.

Question 16

What are the components of phenotypic variation?

Answer 16

VP = VG + VE.

Question 17

What happens when two individuals with two different genes mate?

Answer 17

There are 16 different combinations of gametes produced.

Question 18

What is epistasis?

Answer 18

Interaction between alleles.

Question 19

Fill in the blank: The average phenotype amongst parents can be calculated using the formula (Frequency of PP x 0) + (Frequency of Pp x 1) + (Frequency of pp x 2) = _____ .

Answer 19

Average phenotype.

Question 20

What is phenotypic plasticity?

Answer 20

Interaction with the environment affecting traits.

Question 21

True or False: Continuous traits have a simple genetic basis.

Answer 21

False.

Continuous traits have a complex genetic basis.

Question 22

What does the slope represent in estimating heritability?

Answer 22

Heritability.

Question 23

What is the significance of Mendel’s choice of phenotypes in his experiments?

Answer 23

He chose phenotypes influenced by a single gene.

Question 24

What type of inheritance is shown by traits with recessivity and dominance?

Answer 24

Discrete inheritance.

Question 25

What does a heritability value of 0.642 indicate?

Answer 25

Perfect correspondence between parent phenotype and offspring phenotype

A heritability value of 0.642 suggests a moderate to high genetic contribution to a trait.

Question 26

What is the formula for the average offspring phenotype based on parent phenotype?

Answer 26

Y = b0 + b1X with b0 = 0 and b1 = 1

This indicates a direct linear relationship between parent and offspring phenotypes.

Question 27

How has the heritability of PKU changed over time?

Answer 27

Heritability has declined due to environmental factors

Availability of screening and low phenylalanine diets have reduced the impact of genetics on PKU.

Question 28

What was historically true about PKU?

Answer 28

PKU was genetically determined with high heritability

PKU is caused by inheriting two recessive alleles, leading to the disease phenotype.

Question 29

What factors now influence whether an infant displays the PKU phenotype?

Answer 29

Largely a function of the environment

Environmental interventions can prevent the manifestation of PKU despite genetic predisposition.

Question 30

Fill in the blank: The heritability of a trait is calculated as h2 = _____ / 0.

Answer 30

VG

VG represents the genetic variance contributing to the trait.

Question 31

What does the notation ‘PP’, ‘Pp’, and ‘pp’ represent?

Answer 31

Genotypes of individuals regarding a trait

‘PP’ indicates homozygous dominant, ‘Pp’ indicates heterozygous, and ‘pp’ indicates homozygous recessive.

Question 32

True or False: The slope (b1) in the average offspring phenotype formula can be less than 1.

Answer 32

False

In this context, the slope is equal to 1, indicating a one-to-one relationship.

Question 33

What does VP = 0 indicate in the context of PKU?

Answer 33

Indicates no phenotypic variance under certain conditions

This suggests that environmental factors can eliminate the expression of the phenotype.