Reproduction and Inheritance - Inheritance

Question 1

what is a genome?

Answer 1

the entire dna of an organism

Question 2

what is a gene?

Answer 2

a section of a molecule of dna that codes for a specific protein

Question 3

where are genes located?

Answer 3

the nucleus of a cell, which contains chromosomes which contain genes

Question 4

what is an allele?

Answer 4

an alternative form of gene that codes for a different variation of a specific trait

Question 5

what is a dominant gene?

Answer 5

a variant of a gene for a particular characteristic that will always express itself

Question 6

what is a recessive gene?

Answer 6

a variant of a gene for a particular characteristic that will only express itself when paired with another recessive gene

Question 7

what does homozygous mean?

Answer 7

when an individual has two identical alleles of a gene

Question 8

what does heterozygous mean?

Answer 8

when an individual has two different alleles of a gene

Question 9

what is a phenotype?

Answer 9

a characteristic of an organism

Question 10

what is a genotype?

Answer 10

the allele combination of an organism

Question 11

what is polygenic inheritance?

Answer 11

characteristics that are controlled by more than one gene. most phenotypic features are the result of this.

Question 12

what sex chromosomes do females and males possess?

Answer 12

females: XX
males: XY

Question 13

what is mitosis?

Answer 13

division of a diploid cell producing two cells that contain identical sets of chromosomes

Question 14

when does mitosis occur?

Answer 14

during growth, repair, cloning and asexual reproduction

Question 15

what is meiosis?

Answer 15

division of a cell producing four genetically different daughter cells, each with half the number of chromosomes

Question 16

what happens during mitosis?

Answer 16

• dna replication occurs to form two copies of each chromosome in the cell
• the nuclear membrane breaks down and the chromosomes line up across the centre of the cell
• fibres attach to each set of chromosomes, pulling them to each end of the cell to form two individual nuceli
• cytoplasm and cell membrane divides along with the nucleus, resulting in two identical daughter cells

Question 17

what happens during meiosis 1?

Answer 17

• the cell duplicates its dna so one arm of each chromosome is an exact copy of the other arm
• in the first division, the chromosomes line up in pairs in the centre of the cell
• the pairs are then pulled apart, so each new cell only has one copy of each chromosome
• each cell has a mixture of the mothers and fathers chromosomes

Question 18

what happens during meiosis 2?

Answer 18

• the chromosomes line up again at the centre of the cell and the arms of the chromosomes are pulled apart
• you get 4 haploid gametes with a single set of chromosomes who are all genetically different

Question 19

what causes genetic variation in offspring?

Answer 19

random fertilisation

Question 20

what is the human diploid number?

Answer 20

46

Question 21

what is the human haploid number?

Answer 21

23

Question 22

why could there be variation within a species?

Answer 22

due to genes, environment or both

Question 23

what is a mutation?

Answer 23

a rare, random change in genetic material that can be inherited

Question 24

what is the theory of evolution?

Answer 24

• organisms within the population will show variation via mutations
• the mutated organism that has characteristics allowing them to be better adapted to the environment will have higher a chance of survival
• hence, they will reproduce to pass on these beneficial mutations to their offspring
• as a result, offspring will carry the same beneficial gene, allowing the population over time to be better adapted to the environment

Question 25

how can antibiotic-resistant bacteria develop?

Answer 25

- bacteria will undergo rare and random mutations - bacteria can develop a mutation causing them to be resistant to antibiotics - antibiotic-resistant bacteria reproduce and pass on the gene to offspring - population of antibiotic-resistant bacteria will increase, as other bacteria are killed off by antibiotics