Science - Genetic Variation: key terms

Question 1

Define: DNA

Answer 1

The molecule that carries the genetic instructions. shape; a double helix

Question 2

Define: Gene

Answer 2

Section of a chromosome that codes for one trait
e.g. eye colour

Question 3

Define: Allele

Answer 3

The different forms of a gene
e.g. brown eyes

Question 4

Define: Chromosomes

Answer 4

Thread like structures found in the nucleus that contain long lengths of DNA that holds many genes.

Question 5

Define: Fertilisation

Answer 5

The random fusing/joining of the male and female gametes to produce genetically unique offspring

Question 6

Define: Base sequence

Answer 6

The order of bases (A, T, C and G) that form the genetic code

Question 7

Define: Phenotype

Answer 7

Physical expression (appearance) of the gene/genotype

Question 8

Define: Genotype

Answer 8

The alleles present (an individual carries) for a gene/characteristic/trait

Question 9

Define: Sexual Reproduction

Answer 9

The combining/mixing DNA from two parents (through fertilisation using gametes produced by meiosis) to produce genetically unique offspring
THROUGH SEX!!! ;)))

Question 10

Define: Meiosis

Answer 10

a cell division process that produces four genetically unique gametes with half the number of chromosomes as the parent cell.

Question 11

Define: Crossing Over

Answer 11

During meiosis when DNA is exchanged between homologous chromosomes. This results in new allele combinations and therefore increases genetic variety.

Question 12

Define: Independent assortment

Answer 12

When the homologous pairs line up during meiosis, the arrangement is random. Therefore, alleles will be put together in new combinations in gametes giving more genetic variety.

Question 13

Define: Inheritable Variation

Answer 13

Involves a change in the DNA of gametes so can be passed on to offspring

Question 14

Define: Non-inheritable variation

Answer 14

Is a change in the somatic cells so only affects the organism and cannot be passed onto offspring

Question 15

Define: Homologous Chromosomes

Answer 15

Carry the same genes and one chromosome comes from the mother and one comes from the father.

Question 16

Define: Pure Breeding

Answer 16

Homozygous for a trait (AA or aa)

Question 16

Define: Genetic variation

Answer 16

Differences in the DNA/genes/characteristics of individuals in a species

Question 16

Define: Recessive

Answer 16

The trait will only be expressed if two alleles are present in the genotype (aa)

Question 16

Define: Dominant

Answer 16

The trait is always expressed if the allele is present in the genotype

Question 16

Define: Mutation

Answer 16

A change in DNA (genetic material)

Question 16

Define: Gamete

Answer 16

Sex cell with half the number of chromosomes (used for fertilisation in sexual reproduction) as the parent cell

Question 17

VARPA

Answer 17

• Variation = exits in pop. random mutation
• Adaptation = survival advantages
• Reproduction = favorable adaptations –> reproduce
• Passing on = Fav. alleles passed on to OS
• Allele frequency = Fav. adapt. = common