6.2.1 genetic variation

Question 1

define phenotype

Answer 1

visible characteristics of organism

Question 2

define genotype

Answer 2

genetic make-up of organism

Question 3

cause of phenotypic variation

Answer 3

phenotype influence by genotype & environment

Question 4

what can increase rate of mutation

Answer 4

mutagens

Question 5

types of mutagens (with examples)

Answer 5

• physical agents (eg. x-rays, gamma rays, uv light)
• chemical agents (eg. nitrous acid, benzopyrene)
• biological agents (eg. some viruses, transposons, food contaminants)

Question 6

mutations which happen during gamete formation are:

Answer 6

‣ persistent = transmitted through many generations without change
‣ random = not directed by need from organism

Question 7

when may chromosome mutations occur

Answer 7

during meiosis

Question 8

types of chromosome mutations (may happen during meiosis)

Answer 8

‣ deletion = part of chromosome is lost (contains genes/regulatory sequences)

‣ inversion = section of chromosome may break off, turn 180 degrees & join again (some genes too far away from regulatory nucleotide sequences to be expressed)

‣ translocation = piece of 1 chromosome breaks off & becomes attached to another chromosome

‣ duplication = piece of chromosome may be duplicated (overexpression of genes is harmful as too many of certain proteins/gene-regulating nucleic acids can disrupt metabolism)

‣ non-disjunction = 1 pair of chromosomes/chromatids fail to separate, leaving 1 gamete with extra chromosome, so resulting zygote has extra chromosome (causes down-syndrome)

‣ aneuploidy = chromosome number isn’t exact multiple of haploid number for organism (sometimes chromosomes/chromatids fail to separate during meiosis)

‣ polyploidy = if diploid gamete fertilised by haploid gamete, resulting zygote will be triploid (3 sets of chromosomes) & fusion of 2 diploid games creates tetraploid zygote (many cultivated plants are polyploid)

Question 9

what is genetic variation caused by during meiosis (sexual reproduction)

Answer 9

‣ allele shuffling during crossing over in prophase 1

‣ independent assortment of chromosomes during metaphase/anaphase 1

‣ indendent assortment of chromatids during metaphase/anaphase 2

Question 10

properties of gametes produced by meiosis

Answer 10

• individual
• genetically dissimilar
• haploid

Question 11

what creates genetic diversity during sexual reproduction

Answer 11

= random fusion of gametes

• any male gamete can fuse with any female gamete from organism of same species
• random fertilisation of gametes (already genetically unique) produces genetic diversity among offspring

Question 12

variation caused solely by environment

Answer 12

• speaking with regional dialect
• losing digit/limb or scar (following surgery)

Question 13

example of variation caused by environment interacting with genes

Answer 13

◦ if plants kept in low light after germination/soil contains insufficient magnesium = leaves don’t develop enough chlorophyll & are yellow (plant described as chlorotic/suffering from chlorosis)
‣ plant cannot photosynthesise
◦ chlorotic plants have gene for making chlorophyll, but environmental factors preventing expression of genes