Genetic Variation 1.9

Question 1

Define the role of DNA

Answer 1

DNA carries instructions to the next generation. The base sequence on DNA determines a particular feature and variations on that feature.

Question 2

Define base sequence

Answer 2

The orders of bases (A, T, C and G) that carry the code

Question 3

Define gene

Answer 3

A short length of DNA that carries the genetic code for a particular characteristic or cell activity.

Question 4

Define allele

Answer 4

An alternative/different version of the same gene (can be dominate or recessive).

Question 5

Define phenotype

Answer 5

Physical expression of the genotype

Question 6

Define genotype

Answer 6

Code for the alleles present in the gene

Question 7

Define sexual reproduction

Answer 7

Combining DNA from two parents using meiosis to produce gametes

Question 8

Define meiosis

Answer 8

Cell division that occurs in the testes (males) and ovaries (females). It produces four new cells (gametes) that are genetically different to each other and the parent cell. Cells produced are haploid (they contain half the number of chromosomes that are in the parent cell).

Question 9

Define inheritable variation

Answer 9

Can be passed on to offspring and involves a change in the DNA

Question 10

Define non-inheritable variation

Answer 10

Only affect the organism and not its’ offspring, due to environmental factors

Question 11

Define homologous chromosome

Answer 11

One chromosome comes from the mother and one comes from the father

Question 12

Define pure breeding

Answer 12

Homozygous for a trait (AA or aa)

Question 13

Define fertilisation

Answer 13

Meeting of male and female gametes

Question 14

Define genetic variation

Answer 14

Variety within a population e.g different alleles possible for each gene

Question 15

Define chromosome

Answer 15

A threadlike structure of DNA found in the nucleus of cells. They carry information in the form of genes.

Question 16

Define dominant

Answer 16

The trait will be expressed if present

Question 17

Define recessive

Answer 17

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

Question 18

Define mutation

Answer 18

A change in the base sequence of DNA (could be due to an extra base, incorrect pairing or a missing base in the structure of DNA).

Question 19

Define mitosis

Answer 19

Cell division that occurs whenever more cells are needed (growth and repair). It occurs in somatic (body cells) produces two new diploid cells that are genetically identical.

Question 20

Define nucleotide

Answer 20

Nucleotides for the basic structural unit of DNA. Composed of a base, sugar and phosphate.

Question 21

Define trait

Answer 21

A genetically determined characteristic

Question 22

Define zygote

Answer 22

A fertilised ova (egg) that contains the full set of chromosomes

Question 23

Define base

Answer 23

Parts of DNA involved in pairing. The bases are cytosine, guanine, adenine and thymine.

Question 24

Define the structure of DNA

Answer 24

DNA is in the structure of a double helix. DNA is made up of molecules called nucleotides. Each nucleotide contains a phosphate, a sugar and a base. The sides of the DNA are made of the phosphate and sugar and linked together with the base.

Question 25

What is the relationship between DNA, alleles, genes and chromosones?

Answer 25

…

Question 26

Which mutations may be inherited and which may not?

Answer 26

If it affects somatic cells vs

Question 27

Define haploid and diploid

Answer 27

Haploid, half set of chromosomes, diploid has full.

Question 28

How does meiosis cause variation?

Answer 28

Two ways - crossing over and independent assortment. Crossing over occurs when bit of homologous chromes are exchanged during meiosis. Independent assortment is random and one of a pair of homologous chromosomes goes into a gamete after they line up in pairs during meiosis.