11 Inheritance

Question 1

Define Inheritance

Answer 1

The transmission of genetic
information from generation to generation.

Question 2

Define Chromosome

Answer 2

A thread-like structure of
DNA, carrying genetic information in the form of
genes.

Question 3

Define Gene

Answer 3

A length of DNA that codes for a protein.

Question 4

Define Allele

Answer 4

A version of a gene.

Question 5

Describe the inheritance of sex in humans

Answer 5

Sex is determined by an entire chromosome pair. Females have the XX sex chromosomes whilst males have XY. Father determines sex of child since he is the only one that can pass on the Y chromosome. Half of the sperm will have X chromosome and the other half will have Y. Depending on the sperms chromosome, the sex will be determined.

Question 6

Define a Haploid nucleus

Answer 6

A nucleus containing a single set of unpaired chromosomes, for example in gametes.

Question 7

Define a Diploid nucleus

Answer 7

A nucleus containing two sets of chromosome, for example in body cells.

Question 8

How many chromosomes in a human haploid gamete cell?

Answer 8

23

Question 9

Define Mitosis

Answer 9

Nuclear division giving rise to genetically identical cells.

Question 10

What occurs before mitosis?

Answer 10

The exact duplication of chromosomes.

Question 11

Role of Mitosis

Answer 11

Used for growth as they produce new cells, repair to replace damaged or dead cells, replacement of cells and asexual reproduction as it produces offspring identical to the parent.

Question 12

Define Meiosis

Answer 12

A reduction division in which the chromosome number is halved from diploid cells. Gives rise to cells that are genetically different. Used to produce gametes. Increases genetic variation of offspring by forming new combinations of maternal and paternal chromosomes every time a gamete is made.

Question 13

Define Genotype

Answer 13

The genetic make-up of an organism in terms of the alleles present.

Question 14

Define Phenotype

Answer 14

The observable features of an organism.

Question 15

Define Homozygous

Answer 15

Having two identical alleles of a particular gene.

Question 16

How does pure-breeding occur?

Answer 16

Two identical homozygous individuals breeding together.

Question 17

Define Heterozygous

Answer 17

Having two different alleles of a particular gene.

Question 18

Define Dominant

Answer 18

An allele that is expressed if it is present.

Question 19

Define Recessive

Answer 19

An allele that is only expressed if it is present.

Question 20

Define Variation

Answer 20

Differences between individuals of the same species.

Question 21

Define Phenotypic variation

Answer 21

The differences in features between individuals of the same species caused by both genes and the environment.

Question 22

Define Genetic variation

Answer 22

Differences in features caused by differences in genes.

Question 23

Differences between Continuous and Discontinuous variation

Answer 23

Continuous: results in a range of phenotypes between two extremes (E.g. height).
Discontinuous: results in a limited number of phenotypes with no intermediates. Mostly caused by genes alone (E.g Blood groups).

Question 24

Define Mutation

Answer 24

A change in a gene or chromosome.

Question 25

Causes of Mutation

Answer 25

Exposure to ionising radiation such as gamma rays, X rays and UV radiation.
Chemical mutagens, such as some of the chemicals in tobacco.

Question 26

Describe Natural selection

Answer 26

In any population of organisms, there is variation between them. When they reproduce, the produce more offspring than the environment is able to support. This leads to competition for food and other resources which results in a ‘struggle for survival’. Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce. The alleles resulting in these characteristics are passed on to their offspring at a higher rate. This means in the next generation, there will be a greater number of individuals with better adapted variations in characteristics.

Question 27

Define Evolution

Answer 27

The change in adaptive features of a population over time as the result of natural selection.

Question 28

Define the process of Adaptation

Answer 28

The process resulting from natural selection by which populations become more suited to their environment over many generations.

Question 29

Describe the development of strains of antibiotic resistance

Answer 29

An example of evolution by natural selection.

Question 30

Describe Selective breeding

Answer 30

When a breeder chooses which parent organisms breed together. Usually for desirable features.

Question 31

Differences between Natural and Artificial breeding

Answer 31

Artificial: Humans decide on the characteristics they want from a species and then select the individuals closest to those characteristics to reproduce.
Natural: Results are more unpredictable because individuals best adapted to their environment are selected. They have more offspring and so over time the species develops the characteristics.

Results from artificial selection are more useful to humans whereas the results from natural selection are better adapted to the environment.