INHERITANCE

Question 1

Genotype

Answer 1

Genetic constitution of an organism/combination of alleles the individual posses

Question 2

Phenotype

Answer 2

Expression of the genotype and its interaction with the environment

Question 3

Gene

Answer 3

A length of DNA that codes for a particular protein

Question 4

Gene Pool

Answer 4

All the alleles in a population

Question 5

Chromosome

Answer 5

One long DNA molecules which contains genes

Question 6

Locus

Answer 6

The position of a gene on a chromosome

Question 7

Allele

Answer 7

Alternative version of a gene, (there may be multiple alleles of a single gene)

Question 8

Dominant Allele

Answer 8

The allele always expressed in the phenotype

Question 9

Recessive Allele

Answer 9

The allele that is only expressed in the phenotype in the absence of the dominant allele

Question 10

Co-dominance

Answer 10

When both alleles are being expressed in the phenotype
when alleles are co-dominant, so if they are present they are both expressed in the phenotype, takes place usually when a gene has more than 2 alleles

Question 11

Monohybrid Inheritance

Answer 11

Inheritance of a single gene with two alleles

Question 12

Why Monohybrid Cross ratios may not take place in reality

Answer 12

fusion of gametes is random
Mating is related to chance
Differential mortality

Question 13

Sex Linkage

Answer 13

concerns genes found on the sex chromosomes, X and Y, (X gene will contain the disease)
Males have only one X chromosome (XY) therefore can never be carriers. Females have two X chromosomes (XX) therefore can be carriers. The gametes will be each chromosome, i.e. men have genotype XY, separating them gives you two gametes, X and Y.
Sex Linked diseases that kill children will become extinct as children who are affected will not be able to pass on the disease.
VERY rarely there may be a gene that is existent on the Y chromosome, however this would mean that all males would be affected and no females.

Question 14

Males are more likely to have a sex-linked disease that is recessive

Answer 14

Males have only one alleles, therefore it could be the recessive one
Females need two recessive alleles to have the disease

Question 15

How to prove that a certain condition is on the recessive allele

Answer 15

Affected child produced from unaffected parents

Therefore parents are heterozygous

Question 16

How to prove that a certain condition is on the dominant allele

Answer 16

Affected parents produce unaffected child

Therefore parent are heterozygous (and still affected, therefore allele causing condition is dominant)

Question 17

How to prove a condition is not sex-linked

Answer 17

The condition is on the dominant allele
Affected male (XRY) and unaffected female (XrXr) are producing an affected male (XRY) which is not possible

Question 18

How to prove a condition in on the x-chromosome:

Answer 18

Affected male children from unaffected father

Question 19

Serious diseases caused by dominant alleles are uncommon compared with serious diseases caused by recessive alleles

Answer 19

If it is on the dominant allele, then all individuals with allele of the disease develop the disease, i.e. they become aware of the disease and therefore decided not to have children
If the serious disease is on recessive allele, it may not affect individual, therefore individual will not be aware of the disease and may have children
Some diseases are fatal, yet they are passed on, this may be due to the fact that the disease takes effect in old age, by which time offspring have already been produced.

Question 20

If a recessive allele is causing a hindrance to a species’ ability to compete, then the frequency of the recessive allele will decrease over time, because:

Answer 20

Due to directional selection
The dominant allele has an advantage over the recessive allele, therefore more likely to survive.
Dominant Allele frequency + Recessive Allele frequency = 1; p + q = 1 (this is as long as the two alleles are for the same gene)
Homozygous Recessive frequency + Heterozygous frequency + Homozygous Dominant frequency = 1; p2 + 2pq + q2 = 1

Question 21

Hardy-Weinberg principle

Answer 21

The frequency of alleles will remain constant from one generation to the next providing no mutation, geographical isolation, selection, migration etc. takes place. (The Hardy-Weinberg Principle is actually more of a PREDICTION than a principle)
We cannot do an investigation on the frequency of certain alleles in a group of organisms if one of the organisms is deaf, blind, etc. This is because this organism will not survive and therefore will not pass on allele

Question 22

Assumptions made when using the Hardy-Weinberg equation

Answer 22

No selection
Random mating
Large gene pool
No migration
No mutation
Equally fertile genotypes
Generations do not overlap

Question 23

When studying genetic crosses, you use an animal which

Answer 23

Gives large number of offspring; low sampling error
Short life cycle; results obtained quickly
Male and female easily distinguished for mating
Small size; easy to handle and less space required

Question 24

How there is genetic variation in a sexually reproducing animal

Answer 24

Independent alignment of chromosomes which gives a new arrangement of alleles
Random fertilisation which gives a chance combinations of gametes
Mutations create new alleles