biology b5.1

Allele

A version of the same gene (also known as variant)

Asexual reproduction

A form of reproduction that only involves a single parent and creates genetically identical offspring

Chromosome

À long, coiled molecule of DNA that carries genetic information in the form of genes

Continuous variation

Variation that can take any value between two extremes (height or weight)

DNA

A polymer that is made of two strands twisted around each other forming a double helix. It contains all the genetic information

Diploid

When a cell has a full set of chromosomes

Discontinuous variation

Variation that can only take discrete values (Eye colour)

Dominant

An allele that is always expressed when present. It is represented by a capital letter.

Enzyme

Biological catalysts that increase the rate of chemical reactions

Gamete

Sex cell

Genome

The entire genetic material of an organism

Genotype

The genetic make up of an organism

Haploid

When a cell has half the number of chromosomes

Heterozygous

When a individual has two non identical allèles of a gene

Homozygous

When an individual has two identical allèles of a gene

Meiosis

À form of cell division that produces gamètes. They are not genetically identical and contain half the number of chromosomes

Messenger RNA (MRNA)

À RNA subtype that carries genetic information from the nucleus to the ribosomomes during protein synthesis

Mutation

À random change in DNA which increases variation. They may have a neutral, beneficial or damaging effect on the phenotype.

Nucleus

An organelle found in most eukaryotic cells that contain the cells genetic material and controls the activities of the cell

Phenotype

The physical characteristics of an organism. It is due to interactions between the genotype and the environment.

Punnett square

À grid used to determine potential outcomes of a genetic cross

Recessive

An allele that is only expressed if homozygous

Seed bank

À place where seeds are preserved in order to preserve genetic diversity

Sexual reproduction

Reproduction that involves the fusion of male and female gamètes. This method of reproduction produces genetic variation.

Single gene inheritance

Inheritance of characteristics that are controlled by a single gene

Transcription

The unzipping of the DNA molecule around the gene, copying it to mRNA in the nucleus

Translation

Translating the mRNA sequence to an amino acid sequence during protein synthesis

What causes variation within a species?

Genetic material you inherit from your parents,

Changes in the DNA caused by the environment that you live in

Causes of mutations

Viruses, ionising radiation, chemicals, UV light

Effects of mutations

Cancer, alleles.

What percentage of DNA codes for proteins?

2%

Cell division

When a cell divides to make more cells, the DNA has to make an exact copy of itself

What do cells need to divide for?

Growth and repair, asexual reproduction, sexual reproduction

Interphase

Each chromosome replicates so it contains two identical chromatids

Prophase

Chromosomes become visible by shortening and thickening

Metaphase

The chromosomes align up along the centre of the parent cell

Anaphase

The two chromatids in each chromosome are pulled apart to the opposite poles of the cell

Telophase

There are now two nuclei

Cytokinesis

The cell splits in two to produce two daughter cells, each containing the same chromosomes

What is required for sexual reproduction?

Fertilisation - where 2 gamètes fuse together to make a zygote

What were mendels 3 main conclusions?

Characteristics are determined by hereditary units passed on from parent to offspring

The offspring receives one hereditary unit from each parent

Hereditary units can be dominant or recessive

How many pairs of chromosomes do human body cells have in the nucleus?

23