Genetic Variation

Question 1

Chiasma

Answer 1

The point in which paired chromosomes contact during meosis
OR
The contact point between the two chromatids of a chromosome during meiosis.
OR
a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands.

Question 2

Crossing over

Answer 2

Two homologous chromosomes pair up, creating a homologous pair of chromosomes. The non-sister chromatids swap alleles. Resulting in new combinations of alleles, meaning there is genetic variation.

Question 3

Diploid Cell

Answer 3

A cell that contains a complete set of chromosomes (e.g in humans 46 chromosomes)

Question 4

Haploid Cell

Answer 4

A cell that contains half as many chromosomes as a diploid cell (e.g in humans 23 chromosomes)

Question 5

Gamete

Answer 5

A reproductive cell having haploid number of chromosomes (e.g in females egg and males sperm)

Question 6

Independent Assortment

Answer 6

when homologous chromosomes line up in the equator (centre) of the cell, independently of other pairs. Resulting in a randomised line. They are then separated in segreation which resultings in genetic variation as each gamaete receives one chromosomes, meaning there will be different allees in each gamete.

Question 7

locus

Answer 7

a location a given gene occupies on a chromosome

Question 8

Meiosis

Answer 8

A type of cell division in sexually reproducing organisms that produces gametes and reduces the number of chromosomes in the reproductive cells from diploid to haploid.

Question 9

Segregation

Answer 9

The separation of homologous chromosomes. Resulting in each gamete receiving one allele or chromosome
OR
Each gamete / daughter cell receives a single allele / copy of each gene OR results in unique combination of alleles

Question 10

Mutation

Answer 10

A permanent change to the base sequence of DNA - which may result in a new allele. This causes genetic variation as if the mutation occurs in a gamete it may be passed on to offspring if the gamete is fertilised.

Question 11

Mutagen

Answer 11

An agent that can create a mutation e.g chemicals, radiation etc

Question 12

Co-Dominances

Answer 12

An individual who is heterozygous and expresses both phenotypes associated with both alleles and are equally and independently expressed.

Question 13

Complete Dominance

Answer 13

A relationship between alleles of a single gene, in which one allele masks the phenotypic expression of another allele at the same gene locus.

Question 14

Incomplete Dominance

Answer 14

Neither allele is dominant and the heterozygotes is intermediate in phenotype between the two homozygotes. A heterozygous individual which phenotype is a combination of both alleles phenotype.

Question 15

Multiple Alleles

Answer 15

Two or more alleles present in a species for a particular gene

Question 16

Lethal Allele

Answer 16

Gene mutations result in gene product which is not only functional but also affects the organism’s chances of survival. Lethal alleles are alleles that cause an organism to die when present in a homozygous condition.

Question 17

Pure breeding

Answer 17

A group of identical individuals that always produce offspring of the same phenotype when intercrossed.

Question 18

Test Crossing

Answer 18

crossing an unknown genotype individual with a homozygous recessive individual to determine the unknown individual’s genotype. This is done to determine whether the genotype is heterozygous or homozygous dominate

Question 19

Linked Genes

Answer 19

When two alleles are on the same chromosome and are often inherited together

Question 20

Genetic Diversity

Answer 20

different genetic combinations in an gene pool

Question 21

Gene pool

Answer 21

total genetic makeup (alleles) in an interbreeding population

Question 22

Evolution

Answer 22

the change in characteristics of a population over time

Question 23

Natural Selection

Answer 23

the name for the process by which beneficial phenotypes in a population tend to survive and reproduce while unfavourable phenotypes tend to be lost

Question 24

Bottleneck effect

Answer 24

Is where there is a large reduction in a population due to an environmental change (natural disasters) or human actions

Question 25

Founders effect

Answer 25

Founders effect is when a small group of a population is geographically isolated from the original population or emigrate somewhere else

Question 26

Gene flow

Answer 26

is the process in which individuals emigrate (leave) out of the population or immigrate (arrive) into the population

Question 27

Genetic drift

Answer 27

the frequency of alleles change due to chance, rather than selective pressures

Question 28

Heterozygous

Answer 28

A individual with two different alleles for the same trait

Question 29

Homozygous Recessive

Answer 29

An organism or cell with two recessive alleles for a single trait

Question 30

Homozygous Dominnatn

Answer 30

An organism or cell with two dominant alleles for a single trait.

Question 31

Relationship between gene, alleles DNA and chromosomes

Answer 31

dna.is.genetic.information.A chromosome is a specific strand of DNA, which subdivides into genes. a gene codes for aspecific ascpet/trait, alleles are variations of genes. Genes are built into chromomes which are built into DNA

OR
Alleles are different forms of same gene. Genes are linearly arranged on chromosomes. Chromosomes contain genetic material of cell i.e. DNA. So chemically alleles, genes, chromosomes are all DNA !