b13

Question 1

gametes in plants

Answer 1

pollen and egg cells

Question 2

gametes in animals

Answer 2

sperm and egg cells

Question 3

why is there variation in sexual reproduction?

Answer 3

it is due to the mixing of gametes which leads to variety in offspring. gametes are formed by meiosis

Question 4

what is asexual reprodution

Answer 4

it involves only one parent and no fusion of gametes. theres no mixing of genetic info which leads to identicle offsprings

Question 5

what happens when a cell divides to form gametes?

Answer 5

cells in reproductive organs divide by meiosis. there are copies of the genetic information. the cell divides twice to form 4 gametes each with a single set of chromosomes which are all genetically different from each other.

Question 6

what happens at fertilisation?

Answer 6

gametes join to restore the normal number of chromosomes. this cell then divides by mitosis. the number of cells increases. as the embryo develops, the cell differentiates.

Question 7

what are the advantages of sexual reproduction?

Answer 7

it produces variation in offspring. if the environment changes, this variation gives a survival advantage by natural selection.
natural selection can be speeded up by humans in selective breeding to increase food population.

Question 8

what are the advantages of asexual reproduction?

Answer 8

only one parent is needed. more time and energy efficient as theres no need to find a mate. much faster than sexual reproduction. many identicle offspring can be produced when conditions are favourable.

Question 9

how do malarial parasites reproduce?

Answer 9

asexually in the human host, but sexually in the mosquito.

Question 10

how do fungi reproduce?

Answer 10

asexually by spores but also sexually to give variation

Question 11

how do plants reproduce

Answer 11

they produce seeds sexually, but also reproduce asexually by runners like strawberry plants, or bulb division like daffodils.

Question 12

what is DNA

Answer 12

a polymer made up of two strands forming a double helix. the DNA is contained in structures called chromosomes.

Question 13

what is a gene?

Answer 13

a small secion of DNA on a chromosome. each gene codes for a particular sequence of amino acids to make a specific protein.

Question 14

what is a genome?

Answer 14

the genome of an organism is the entire genetic material of that organism. the whole human genome has been studied and this will have great importance for medicine in the future

Question 15

what is the structure of DNA?

Answer 15

a polymer made from 4 different nucleotides. each nucleotide consists of a common sugar and phosphate group, with one of four different bases attached to the sugar ( T A G C)
DNA is a polymer made up of repeating nucleotide units.

Question 16

what is the code for an amino acid?

Answer 16

a sequence of three bases. the order of the bases controls the order in which amino acids are assembled to produce a particular protein.

Question 17

describe protein synthesis

Answer 17

proteins are synthesised on ribosomes, according to a template. carrier molecules bring specific amino acids to the growing protein chain in the correct order. when the protein chain is complete, it folds up to form a unique shape. this unique shape enables the proteins to do their job as enzymes, hormones or forming structures in the body like collagen.

Question 18

what are mutations?

Answer 18

random changes that occur in the sequence of DNA bases in a gene or chromosome.
- they happen continuously
- mutations in a gene can sometimes lead to a change in the protein that the gene codes for.
- mutations can affect how genes are expressed.

Question 19

allele

Answer 19

different versions of a particular gene

Question 20

chromosome

Answer 20

a long, coiled molecule of DNA that carries genetic information in the form of genes

Question 21

dominant

Answer 21

an allele that is always expressed, represented by a capital letter

Question 22

gamete

Answer 22

sex cells with half the number of
usual chromosomes

Question 23

gene

Answer 23

a section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein

Question 24

heterozygous

Answer 24

when someone has two different alleles

Question 25

homozygous

Answer 25

when someone has two identicle alleles

Question 26

genotype

Answer 26

combination of alleles that control each characteristic

Question 27

phenotype

Answer 27

an organism’s observable characteristics. due to interactions of the genotype and the environment

Question 28

reccessive

Answer 28

an allele that is only expressed ub the absence of a dominant allele/ represented by a small letter.

Question 29

what is cystic fibrosis?

Answer 29

a disorder of cell membranes that is caused by a recessive allele

Question 30

what is polydactyly

Answer 30

having extra fingers or toes which is caused by a dominant allele

Question 31

what are the arguments for embryo screening?

Answer 31

it can avoid suffering by stopping children from being born with genetic disorders
the treatment for disorders costs governments and taxpayers a lot of money
there are laws in place to stop embryo screening from being abused

Question 32

what are the arguments against embryo screening?

Answer 32

it could imply that people with genetic disorders are undesirable which is not fair or true.
it is very expensive and therefore not available to all

Question 33

sex chromosome for females

Answer 33

xx

Question 34

sex chromosome for males

Answer 34

xy