Topic 3- Genetics Flashcards
Definition of sexual reproduction
Fertilisation of a female sex cell by a male sex cell
Definition of asexual reproduction
Producing clones
(offspring that are genetically identical to the parent)
Zygote
- A fertilised egg cell
* A single cell made by the fertilisation of two gametes
Gamete
A sex cell produced by meiosis
Eg. Sperm, egg, pollen
Meiosis
Nuclear division that reduces the number of chromosomes by half
Chromosome
One molecule of DNA
For example in humans they’re in pairs, one from the mother and one from the father
DNA
Deoxyribonucleic acid
The genetic molecule
Haploid
• One set of a species chromosomes
Eg. Humans written as n=23
Diploid
The chromosomes come in pairs
Eg. Humans written as 2n=46
Genes
A section of DNA that makes a chromosome, that codes the instructions to make a protein
Proteins
Polymers of amino acids
Often an enzyme
Nucleotides
Basic building block of DNA
Made up of sugar,phosphate and nitrogenous base
Chromatin
Uncoiled chromosomes
Alleles
Different versions of a single gene
Eg. The gene for human eye colour has 2 alleles (brown and blue)
Parental phenotype
Characteristic of the parent
Eg. Purple flower for a pea plant
Parental genotype
Which alleles for the gene of the phenotype does the parent have
Eg. A parent pea plant with purple flowers may have a genotype of Rr
How are dominant genotypes symbolised?
As a capital letter
Eg. Rr the capital R is the dominant genotype
How are recessive genotypes symbolised?
With a lower case letter
Eg. Rr, the lower case R is the recessive genotype
Homozygous
Has the same alleles
Eg. RR
Heterozygote
Has different alleles
Eg.Rr
Pure breeding
Means an individual has the same alleles for a gene
It is homozygous and has no genetic variation
How many sex chromosomes does a human have?
1 pair of chromosomes are the sex chromosomes
How many autosomes does a human have?
22 pairs are ordinary chromosomes called autosomes
What are the different blood groups
A, B, AB or O
Sex linked genetic disorder
Where the position of the gene that causes the disorder is on the sex chromosomes and is on the sex chromosomes region of the X chromosome that is absent on the y
Example of a co dominant blood group
AB
Harmful mutations
A change in the base sequence that stops the gene from being able to code for a functional protein (usaully an enzyme)
A whole chromosome mutation
A section of chromosome is lost or is added to another chromosome
Eg. X and Y chromosome
Muation
A mutation is a change in the sequence of a gene
Where do mutations come from?
1) during the replication of DNA
2) UV damage, x-ray damage, gamma ray damage
3) mutagenic chemicals
3 types of muation
- neutral mutation (have no affect on phenotype)
- harmful mutations
- a whole chromosome mutation
Stages of meiosis
- DNA is duplicated
DIVISION 1
-chromosomes line up in the centre of the cell
-the pairs are pulled apart so each new cell only has one copy of each chromosome
-each cell has a mixture of the mother’s and father’s chromosomes
DIVISION 2
-chromosomes line up in the centre again
-chromatids are pulled apart
