B5.1

Question 1

What is the phenotype?

Answer 1

The appearance of an organism

Question 2

What is variation?

Answer 2

Differences within a species

Question 3

What is genetic and environmental variation?

Answer 3

Genetic - genetic material you inherit from your parents (eye colour, blood group, genetic disorders)
Environmental - the environment in which you live in
Some variation is affected by both (height)

Question 4

What is continuous and discontinuous variation?

Answer 4

Discontinuous variation - distinct characteristic that can be grouped (blood group, gender), bar chart represents this data
Continuous variation - characteristic can be between multiple values (skin colour, leaf SA), histogram shows the data

Question 5

What is asexual reproduction?

Answer 5

When the offspring is genetically identical to the parent cells
Many plants asexually reproduce
Only requires one parent

Question 6

What is sexual reproduction?

Answer 6

Requires two parents
Genetic material is taken from both
Offspring produced are not identical to them
Sexual results in variation

Question 7

What are gametes?

Answer 7

Sex cells
Sperm and egg cells for humans
Pollen cells (male) and egg cells for plants

Question 8

What is fertilisation?

Answer 8

When the gametes fuse together

Question 9

What are the advantages and disadvantages of asexual reproduction?

Answer 9

Advantages:
- if the parent is well adapted to an area, the offspring will share an identical set of characteristics
- only one parent needed (animals wouldn’t need to find a mate, pollination wouldn’t be needed for plants) so reproduction is faster
- larger number of offspring produced quicker
Disadvantages:
- adverse changes to the biotic or abiotic factors may destroy the species

Question 10

What are the advantages and disadvantages of sexual reproduction?

Answer 10

Advantages:
- variation in offspring leads to adaption in a species required to cope with environmental changes
Disadvantages:
- requires two parents
- is slower eso fewer offspring are produced

Question 11

What is a diploid cell?

Answer 11

Contain two sets of each chromosome
In humans they contain 46 chromsomes

Question 12

What are haploid cells?

Answer 12

Gametes are haploid
Only have one of each chromosome
23 in humans

Question 13

What happens during fertilisation?

Answer 13

1) two haploid gametes join together
2) from a diploid cell called a zygote
3) the zygote will divide many times by mitosis to produce a new organism

Question 14

What is a genome?

Answer 14

The entire genetic material of an organism
All individuals have a unique genome except for identical twins

Question 15

How are gametes made?

Answer 15

By a type of cell division called meiosis
Results in 4 genetically unique gametes

Question 16

What happens during meiosis?

Answer 16

1st STAGE:
1) chromosomes are copied
2) these chromosomes line up along the middle of the cell in pairs (one from mother, one from father)
3) one member of each pair is pulled to opposite ends of the cell (when they’re pulled apart, often sections of DNA are swapped)
4) the cell then divides into two
5) two seperate cells are formed
2nd STAGE:
6) chromosomes line up along the middle of each of the two new cells
7) each chromosome is now pulled in half. A single copy of each chromosome foes to opposite ends of the cell
8) each cell then divides into two to produce 4 haploid cells

Question 17

What are alleles?

Answer 17

Different forms of the same gene

Question 18

What is the genotype?

Answer 18

The combination of alleles present in an organism

Question 19

What are the different genotypes?

Answer 19

Homozygous dominant - two copies of the dominant allele
Homozygous recessive - two copies of the recessive allele
Heterozygous - different versions of a gene (Bb)

Question 20

What are the steps to do a genetic cross?

Answer 20

1) state the phenotypes of both parents
2) state the genotype of both parents
3) state the gametes of each parent (normally in circles)
4) use a punnett square to show the results of the fusion of gametes
5) state the percentage of the genotype produced
6) state the phenotype shown in the offspring

Question 21

What is the chromosome for a female and male?

Answer 21

XX = female
XY= male
The father is the one determines the gender as each gametes either has an X or Y chromosome
50% chance of boy or girl

Question 22

What is a mutation?

Answer 22

Occurs when the sequence of DNA bases is altered
Occur spontaneously
Ionising radiation increases the chance of a mutation occuring

Question 23

What are the dangers of mutations?

Answer 23

• cause cancer, when cells grow and divide uncontrollably
• cause production of abnormal protein channels that don’t function properly, cystic fibrosis
• cause different shaped protein molecules to be made

Question 24

Can mutations be beneficial?

Answer 24

Some can be neutral, not good or bad (inability to roll your tongue)
- mutations in bacteria can enable them to be resistant to antibiotics which increases their chance of survival

Question 25

What are the different types of mutations?

Answer 25

Inserted - a base is added, extra amino acids are made so codon will change and protein made will change
Deletion - bass is deleted, less amino acids, codons will again change
Changed - Base is altered, same number of amino acids, codons remain the same except the mutated one

Question 26

What is the history of genetics?

Answer 26

Too long to write
Look at book 4/11 of textbook p.g 164