heredity

Question 1

gene

Answer 1

a unit of inheritance on a particular locus of a chromosome.
it is made up of a sequence of nucleotides that codes for a specific protein that controls a certain characteristic

Question 2

alleles

Answer 2

alternative forms of a same gene
they occupy the same positions on a homologous chromosome

Question 3

chromosome

Answer 3

has many genes along its length

Question 4

phenotype

Answer 4

the physical appearnace of an organism

Question 5

genotype

Answer 5

the genetic make up of an organism

Question 6

homologous chromosomes

Answer 6

a pair of chromsomes that have the same shape, length and same order of gene loci

Question 7

gene loci

Answer 7

position of a gene on a particular chromsome

Question 8

homozygous

Answer 8

if two alleles containing the same trait are identical

Question 9

heterozygous

Answer 9

if two alleles containing the same trait are different

Question 10

pure bred

Answer 10

indiviuals that are homozygous at a particular gene locus

Question 11

selfing

Answer 11

fusion of nuclei of female gamete and nuclei of male gamete from the same individual

Question 12

co-domimance

Answer 12

when both alleles controlling a trait equally expresses themself in a phenotype in an organism in the heterozygous condition

Question 13

diff between AS and NS (5)

Answer 13

AS:
- varieties produced by selective breeding
- selection force is by man
- relatively fast process
- positive to man
- parents are consciously chosen for desirable traits

NS:
- varieties produced by mutations
- selection force is envt
- v slow process
- negative or positive to man
- parents are not consciously chosen

Question 14

diff btwn discontinuous variation and continuous variation (4)

Answer 14

dis:
- a few clear cut phenotypes
- contrlled by 1 or few genes
- genes dont show addtiive effect
- not affected by envt conitions

cont:
- deals with a range of phenotypes
- controlled by many genes
- show additive effect
- affected by envt condtiions

Question 15

mutagens

Answer 15

radiation: uv rays, xray, gamma ray, alpha and beta radiation
chemicals: lysergic acid diethylamine, mustard gas, formaldehyde

Question 16

fromation of new species

Answer 16

Even though there are high reproductive rates, number of organisms in a population remains instant due to enironemntal factors such as competition for resources and predation
Mutation genes may result in formation of new alleles and some of tem may be advantageous
able to camouflage more?? context
When competition arises, nature selects those that have more advantageous favorable traits to survive such as adaptable to changes in environment, disease resistant, more competitive
so more of them survive as less (context) of them die/are eaten
those with the more advantageous favorubal traits will survive to repoudctive age and reproduce and pass down their favourable traits to their offspring
As a result, the frequency of these traits will increase in the population
After many years, new traits form and gives rise to new species

Question 17

artificual selection

Answer 17

Method used by man to purposefully produce offsprings with desirable traits by intentionally choosing those exhibiting the desirable traits
Those with desirable traits are artificially selected by selective breeding
Cross breed two animals -> hybridisation -> new variety that carries both desirable traits
To increase chances of the organism inheriting both traits -> inbreeding -> select two organisms that are closely related
-ve effect: increase inherited diseases

Question 18

down’s syndrome

Answer 18

Change in chromosome number - chromosome mutation during meiosis 1 or 2
1 extra copy of chromosome 21
47 chromosomes in diploid cells
Mental retardation, heart defects

a person has 2 sets of HC, each inherited from a parent. an extra set of chromosome (2set) is oackaged within a single gamete. zygote formed when this gamete fuses with another gamete -> 3 sets of chromosome 21

Question 19

sickle-cell anaemia

Answer 19

Change in structure of gene in DNA - gene mutation
caused by recessive allele
sickle cell sahped red blood cell
RBC unable to transport oxygen at a faster rate
ppl die at younger age

Question 20

multiple alleles def

Answer 20

when a gene controlling a particular trait has 3 or more alleles
e.g. blood group

Question 21

does natural selection lead to gene mutation occuring?

Answer 21

NO

Question 22

mutations benefits

Answer 22

increase genetic variation to adapt to envt conditions
evolution bc of frequncy imcrease

Question 23

mutation meaning

Answer 23

the chnage in nucleotide sequenc of gene, resukting in expression of a polypetide that differs frm nonral polypeptide