Biology- Genetics

Question 1

Define DNA

Answer 1

A polynucleotide that codes for amino acids.

Question 2

Define chromosome

Answer 2

Threadlike structure made form protein and DNA in which genetic (hereditory) information is passed from one generation to the next.

Question 3

Define Gene

Answer 3

Section of DNA on a chromosome coding for one or more polypeptide.

Question 4

Define Allele

Answer 4

An alternative form of a gene located at a specific position.
An allele is a different form of a gene.

Question 5

Define Genome

Answer 5

Minimum group/set of chromosomes derived form a gamete.

Question 6

Define Locus

Answer 6

The location/position of a gene on a chromosome

Question 7

Define Genotype.

Answer 7

The genetic make up of an organism- what alleles are present for a particular gene.

Question 8

Define Phenotyoe

Answer 8

Any observable characteristic of an organism- physical or biochemical.
Results from expression of an organisms genes and environmental factors.

Question 9

Define Homozygous

Homozygote

Answer 9

An organism where identical alleles of the gene are present on both homologous chromosomes.

Question 10

Define Heterozygous

Heterozygote

Answer 10

For a particular gene when two different alleles occupy the genes position of homologous chromosomes.

Question 11

Define Recessive

Recessive allele

Answer 11

An allele that produces its characteristic phenotype only when it’s paired allele is identical- homozygous.

Question 12

Define Dominant

Dominant allele

Answer 12

An allele that produces the same phenotype whether it is paired allele is identical or different, it is always expressed.

Question 13

What are the first Filial (F1) generation?

Answer 13

The offspring to the parent organisms are the F1 generation.

Question 14

Define Monohybrid inheritance.

Answer 14

The inheritance of a characteristic/ one allele pair of one gene.

Question 15

Define Dihybrid inheritance.

Answer 15

Where 2 alleles from 2 different genes located on different chromosomes are inherited.

Question 16

What is Mendels law of Independent assorment?

Answer 16

Each member of a pair of alleles may combine randomly with either of another allele pair.

Question 17

Define Codominance.

Answer 17

Condition in which both alleles for one gene in a heterozygous organism contributeto the phenotype.
Both alleles are expressed in the phenotype.

Question 18

Define the term “Multiple Alleles”

Answer 18

Where a gene has more than 2 possible alleles.

Eg. Blood group
Immunoglobulin gene (gene I) has 3 alleles
I^A I^B I^O

Question 19

What are the ratios of offspring of monohybrid and dihybrid inheritance?

Answer 19

Monohybrind inheritance- 3:1
Dihybrid inheritance- 9:3:3:1
If the ratio is different then consider the possibility of co-dominance.

Question 20

What are the Sex chromosomes for Male and Female?

Answer 20

Male- x,y chromosomes

Female- x,x chromosomes

Question 21

DEfine sex-linked inheritance

Answer 21

Any gene that is carried on either the x or y chromosome is sex linked.
The pattern of inheritance that many result from a mutant gene located on either the x or y chromosome.
(eg. Disease such as haemophilia)

Question 22

Define Autosomal linkage.

Answer 22

Where any two or more genes are carried on the same autosome is called autosomal linkage.
Autosome- Chromosomes (22 of the 23 chromosomes) that aren’t sex chromosomes.

Question 23

Define Epistasis.

Answer 23

Epistasis arises when the allele of one gene affects or masks the expression of another in the phenotype.

Question 24

Define the Hardy-Weinburg Principle.

Answer 24

The allele and genotype frequencies in population remain constant from generation to generation when in the absence of evolutionary influences.

Question 25

What is the Hardy-Weinburg Equation?

Answer 25

Frequency of Dominant allele= p
Frequency of Recessive allele= q

principle: p+q=1
Equation: p^2+2pq+q^2=1

Question 26

Define gene pool.

Answer 26

All the alleles of all individuals in a population at one time.

Question 27

Define allele frequency.

Answer 27

How common a specific allele is within a gene pool on a scale of 0 to 1.
No presence ——–> 100% presence

Question 28

What assumptions are made when using the Hardy-Weinburg principle?

Answer 28

• Large population
• No migration
• No mutations
• No selection/selective pressures
• Random mating (allele cross)

Question 29

What is the Chi Squared test for?

Answer 29

Chi-Square Test. Chi-square is a statistical test commonly used to compare observed data with data we would expect to obtain according to a specific hypothesis.
Used to compare allele ratios both observed and expected.

Question 30

What does a small Chi Squared test mean?

Answer 30

If Chi Squared is smalle that the critical value then there is no significant difference between the expected and observed values.
Therefore there is a greater than 5% probability that the difference in results between the expected and observed values occurred by chance so there is no statistical difference in the expected and observed values.

Question 31

What does a large or small Chi squared mean?

Answer 31

Small Chi Squared = Fits ratio expecting

Large Chi squared = Does not fit expected ratio.

Question 32

From which phenotype can you always tell the genotype?

Answer 32

Recessive allele

Phenotypes expressed by homozygous recessive allele