Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Genes which code for the same characteristic can be found at the same locus. We call
matching pairs alleles.
An allele can be dominant or recessive. We represent dominant genes with a capital
letter (e.g. B) and recessive genes with a lower case letter (e.g. b)
Heterozygous - having dissimilar alleles at corresponding loci.
Homozygous - having identical alleles at corresponding loci.
Phenotype ­ the words to describe a characteristic.
Genotype ­ the letters used to describe the genes.…read more

Page 3

Preview of page 3

Here's a taster:

Monohybrid means that it is limited to 1 gene. However 1 gene = 2 alleles.
Example (1):
Huntingtons disease is an inherited disease which affects the brain and nervous
system. Symptoms do not arise until a person is between 35-45 years old. By this
time that person may have had children and could have passed on the "faulty" gene.
It is caused by a DOMINANT gene.…read more

Page 4

Preview of page 4

Here's a taster:

Sex is determined by sperm. Eggs contain X chromosomes ONLY. Sperm will contain
either an X or a Y.
Females are always XX.
Males are always XY.…read more

Page 5

Preview of page 5

Here's a taster:

Mitosis occurs in all organisms and is a process of asexual reproduction in which the
cell divides in 2, producing a replica with an equal number of chromosomes (2
diploid daughter cells). This process makes all cells other than sex cells (somatic
Cell division by mitosis is used for growth, repair, cloning and asexual reproduction.…read more

Page 6

Preview of page 6

Here's a taster:

only occurs in the reproductive organs and the cells created are sex cells: female egg
cells or male sperm cells.
humans the diploid number of chromosomes is
46 and the haploid is 23.
Diploid cells are found in all places in the body (except the sex cells).
Human egg and sperm cells are the only haploid cells in the body, with 23
chromosomes each.
Random fusion of the male and female gametes contributes to genetic variation of
offspring.…read more

Page 7

Preview of page 7

Here's a taster:

The difference in the appearance of individuals in a species, is because those
individuals have different genotypes and they're surviving and living in different
Some genetic variation (discontinuous
variation) is entirely due to variations in
genes. An example of this is blood
Some genetic variation is due to both
genes and the environment in which you
+ live.…read more

Page 8

Preview of page 8

Here's a taster:

Natural Selection ­ when a plant or animal has an advantage over its competitor it is
more likely to breed and pass on the useful characteristic.
This characteristic may have come about by a rare beneficial mutation, which has
helped the animal/plant to compete and survive. If this is the case, it will be passed
on to the next generations and over time this mutation may become a common gene in
the population.
1) Individuals produce genetically diverse offspring.…read more


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »