B5.1 Inheritance

Question 1

what is variation?

Answer 1

the differences between individuals of the same species - cause by genetic + environmental factors

Question 2

What is a genotype?

Answer 2

the genes / alleles that you possess - 1 inherited from each mum + dad for each characteristic

Question 3

What is a phenotype?

Answer 3

how genotype is expressed - physical appearance - can be affected by environment (e.g. hair colour)

Question 4

Dominant allele

Answer 4

stronger allele - usually darker colour - Capital letter

Question 5

recessive allele

Answer 5

weaker allele - lighter colour - lowercase letter - only shown in phenotype if no other dominant alleles are present

Question 6

Homozygous

Answer 6

when both alleles are same for a characteristic - OO, oo, AA, aa, BB, bb

Question 7

heterozygous

Answer 7

2 different alleles for a characteristic - Ao, Aa, Bb

Question 8

inherited variation

Answer 8

children inherit characteristics from their parents

Question 9

Environmental variation

Answer 9

characteristics are affected by surroundings

Question 10

Discontinuous variation

Answer 10

• distinct categories - e.g. blood group, eye colour, finger prints, tongue rolling
• tends to be qualitative
• controlled by a few genes
• unaffected by environment
• e.g. bar graph

Question 11

Continuous variation

Answer 11

• no distinct categories (e.g. line graph)
• e.g. height, weight, heart rate, hair colour, finger / leaf length
• tends to be quantitative
• controlled by lots of genes
• strongly influenced by the environment

Question 12

asexual reproduction advantages

Answer 12

• if parents well adapted to area so will offspring - natural clones
• 1 parent needed - animals don’t need find partner, plants don’t require pollination - doesn’t require gametes
• reproduction = faster - large numbers offspring produced quickly
• many plants do this

Question 13

asexual reproduction disadvantages

Answer 13

• adverse changes to environment may destroy the species - all organisms affected

Question 14

asexual reproduction example

Answer 14

• strawberry / spider plant - send out runners over ground - runners sprout roots at various intervals - new plants grow - once new plant is established, runners die + rot away

Question 15

Sexual reproduction advantages

Answer 15

• variation in offspring leads to adaptations in species - adverse changes in environment will not really affect the species
• organisms that survive (survival of the fittest) can produce more offspring with adapted genes - allowing population to continue

Question 16

sexual reproduction disadvantages

Answer 16

• requires 2 parents

- reproduction is slower - fewer offspring

Question 17

how does sexual reproduction work?

Answer 17

when nucleus of sperm cell fuses with nucleus of egg cell - egg is fertilised (zygote) - genes from male + female are in fertilised egg which divides and grows in uterus

Question 18

what is the diploid number?

Answer 18

46 chromosomes in most human body cells

Question 19

what cells contain only half the number of chromosomes?

Answer 19

haploid number - gametes

Question 20

where does mitosis occur?

Answer 20

in all somatic body cells during asexual reproduction - results in 2 genetically identical daughter cells

Question 21

what does meiosis produce?

Answer 21

gametes - haploid cells

Question 22

how many cells are produced from meiosis?

Answer 22

4 cells produced - 2 divisions

Question 23

what is a gene?

Answer 23

a length of DNA that contains the code for a specific protein

Question 24

what is an allele?

Answer 24

different versions of a gene

Question 25

where is DNA held?

Answer 25

in chromosomes

Question 26

what is the female sex chromosome

Answer 26

XX

Question 27

what is the male sex chromosome

Answer 27

XY - Y is shorter

Question 28

describe the process of meiosis

Answer 28

• diploid cell - 23 pairs of chromosomes - each chromosome makes an identical copy of itself
• one set of chromosomes goes to each daughter cell
• further cell division - 1 chromosome from each pair goes into each of the 4 sex cells that are made haploid

Question 29

when does a mutation occur?

Answer 29

when sequence of DNA bases is altered

Question 30

what may mutations cause?

Answer 30

genetic variants - different versions of alleles

- mutations occur spontaneously

Question 31

do mutations affect an organisms phenotype?

Answer 31

not normally but it can

Question 32

are the mutations that cause a change in phenotype harmful?

Answer 32

most are - some are neutral and a few are beneficial

Question 33

what causes mutations?

Answer 33

some chemicals greatly increase chance of mutations occurring - e.g. ethanol, benzene
- ionising radiation - e.g. UV from sun, x-rays

Question 34

how can a mutation change an organisms phenotype?

Answer 34

if mutation occurs in gene - DNA bases may be changed, added or deleted

• sequence of bases are changed
• mRNA also changed and order of amino acids may change
• TMT protein produced may fold incorrectly + form a diff shape
• if protein is an enzyme, the reaction would no linger be able to be catalysed