Key Words Flashcards
What is DNA ?
Deoxyribonucleic (DNA) it is the molecule in our nucleus that carries around our genetic code .
How many chromosomes are in an egg and sperm ?
23.
What are the three steps of fertilisation
The egg and sperm meet. The fertilise and become a zygote. Then it becomes a embryo.
How many chromosomes are in a sex cell?
46.
How many chromosomes are in a normal cell?
23.
What is a chromosome ?
A length of DNA.
Where are chromosome’s arranged ?
In the nucleus .
What is along each chromosome ?
Along the length of each chromosome are coding regions called genes. Each gene codes for a specific protein – which give us our unique characteristics.
What is a gene ?
Genes are small sections of chromosomes (DNA) that code for a particular characteristic.
True or false Genes contain a code that code for a particular sequence (chain) of amino acids?
True
What is a allele ?
An allele is a different form of a gene.
What can some alleles do ?
They can make your eye colour and your hair colour.
What are Dominant and Recessive alleles?
Dominant alleles are always expressed if they are
present.
• Recessive alleles are only expressed if there are 2
recessive alleles present.
If two alleles are the same what would they be called?
homozygous alleles.
If two alleles are different what would they be called ?
heterozygous alleles.
Asexual reproduction
Asexual reproduction is a method of reproducing without sex and therefore with out sex cells (gametes). The simplest form of asexual reproduction is binary fission.
Sexual reproduction
Sexual reproduction requires two individuals and the production and fusion of sex cells (gametes). The gametes are produced by meiosis so there are several possible combinations of genetic information when the gamets fuse to create a new life. Because of this there is often a lot of variation in offspring produced by sexual reproduction.
In humans the male gamete is the sperm, the female gamete is the egg (ovum). The following diagrams show the structure of the reproductive systems in males and females. Sperms are made in the testes, eggs (ova) are made in the ovaries.
