Human bio

DNA

deoxyribonucleic acid. 2 main functions: To carry genetic information and coding to produce proteins

Nucleotide

The basic structural unit of DNA, consisting of a deoxyribose sugar, a phosphate and a nitrogen base

Gene

A section of DNA, that codes for a particular trait

Chromatin

Disorganised DNA in the nucleus

Chromosome

Thin thread like structures that store DNA, to form a rod-like structure that contains the genes of an individual

 

DNA Replication

 

The process by which a DNA molecule forms an exact copy of itself

Protein

Controls the characteristics and functions of the body

Helicase

Enyme responsible for separating the two sides of the DNA molecule. Stage 1 in DNA replication. Responsible for unzipping the DNA

Polymerase

Enzyme involved in attaching loose nucleotides to the exposed DNA strand. Stage 2 in making the new DNA, connects the bases together

Ligase

Enzyme involved in repairing the bonds that hold the backbone of the nucleotides together to form DNA. Stage 3 in the making of the new DNA strand it glues the bases that the polymerase put together.

Allele

An alternative form of a gene that occurs at a given point in a chromosome. Letters

Dominant

Where one allele masks the effect of the alternative allele. TT Tt

Recessive

The allele which is only shown if it is not masked by the effects of a dominant allele. tt

Genotype

The genes present in an individual, usually represented by letters eg. RR, Rr, rr.

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Phenotype

The physical appearance of an individual as determined by its genotype

eg. Tongue rolling and non tongue rolling
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Homozygous

Where an individual has two identical alleles for a given gene. TT tt

Heterozygous

Where an individual has two different alleles for a given gene. Tt

Punnett square

A table used to solve genetic problems

Sex-linked trait

A trait controlled by a gene found on a sex chromosome (usually the X chromosome).

X chromosome

One of the sex chromosomes; carries many genes. The big one

Y chromosome

The smaller sex chromosome; carries fewer genes.

Female Chromosomes

XX

Male Chromosomes

XY

X-linked inheritance

When a gene is located on the X chromosome.

Carrier

A person who has one copy of a faulty gene but does not show symptoms.

Affected

A person who shows the trait or disease.

Pedigree

A diagram that shows how a trait is passed through a family.

Generation

A level in a pedigree (e.g. grandparents, parents, children).

Inheritance pattern

The way a trait is passed from parents to offspring.

Helicase number

1

Polymerase number

2

Ligase number

3

A

Adenine

T

Thymine

G

Guanine

C

Cytosine