Genes, Chromosomes, Cell division and variation Flashcards
What is DNA?
DNA is the instructions for building all proteins for an organism, it controls the cells functions etc.
What is DNA short for
DeoxyriboNucleic Acid
Describe the structure of a DNA (4 points)
It’s in a double helix shape. These strands which form the double helix are phosphate and ribose, which form the backbone of the DNA. It’s also made up of four building blocks, which come in pairs: A-T and C-G, these are a.k.a base pairs. There are many of these in a DNA structure
What do the bases do?
They instruct the sequence of amino acids in a protein, like an enzyme.
What is a gene?
A gene is a length of DNA which codes for a protein
What do the proteins in the gene do?
They control chemical reactions, growth, colouration and all inheritab;e characteristics e.g. hieght
How many bases code for one amino acid?
3 bases
What is a chromosome
A rod which comes in pairs (unless it’s a gamete) which carries DNA. It’s made up of DNA and histones
Where do the chromosomes come from?
One form father, one form mother. There’s a pair of genes in each nucleus, as genes controlling a specific characteristics are situated at the same point on each homogolous chromosome
How many chromosomes do humans have
23 pairs
What are 23 pairs of chromosomes referred to as
Diploid cells, haploid cells only contain 23
Which cells are haploid?
Gamete cells e.g. sperm and ovum
What is cell division by mitosis?
Two genetically identical daughter cells produced, involves on e division of a cell, it produces diploid cells acorss the body and keeps the same number of chromosomes in the cell. It occurs throughout a human.
What is cell division by meiosis?
Produces four non identical daughter cells, involves two cell divisions and produces haploid cells in humans. It’s only used to produce gametes.
What is variation
The difference between individuals from the same parents. It’s important for evolution to occur.
