Topic 3 Genetics: Meiosis, DNA structure, DNA extracture, inheritance Flashcards
What is meiosis?
Meiosis produces haploid non-identical sex cells, or gametes. These fuse to form a diploid fertilised egg during fertalisation. Meiosis produces sperm and egg cells in animalls and pollen/egg cells in plants.
What does meiosis produce?
meiosis results in the production of 4 daughter cells, each with half the number of chromosomes and this results in the formation of genetically different haploid gametes.
What is DNA?
DNA is polymer, made of many smaller units called nucleotides. A nucleotide is made up of a sugar and a phophate group, with one of four different bases (A,C,T,G) attatched.
What is the name of the DNA structure?
The nucleotides join together forming two strands, which turn into a double helix structure. The double helix is held together by weak hydrogen bonding between base pairs; A always with T and C always with G.
What is DNA for?
It carries the genetic code, which determines characteristics of a living organism.
What is a gene?
A small section of DNA in a chromosome; each gene codes for a particular sequence of amino acids in order to make a specific protein. Its the unit of Heridity.
What is heridity?
Genetic information which determines an organisms characteristics, passes on from one generation to another.
Whats a genome?
The genome is one copy of all an organisms DNA. In humans this is all the DNA that makes up the 23 pairs of chromosomes found in all diploid body cells. This is all the cells except sex cells or gametes, which only have half of a persons genome.
How do you extract DNA from fruit? (e.g. Kiwi)
1) Peel skin from half a kiwi fruit and mash it up
2) Mix a teaspoon of salt and a small volume of washing up liquid into the fruit
3) Gently heat this mixture at about 60 degrees for 5 minutes
4) Filter the mixture and retain only the filtrate
5) cool using an ice bath and gently poor chilled ethanol onto the top of the filtrate
You will see strands of DNA with bubbles in them at the boundary between the filtrate and the chilled ethanol.
notes
to enable genes to code for proteins, the bases A,T,G and C get together in triplets. Each triplet codes for one particular amino acid, amino acids are made in the number and order dicatated by the number and order of the base triplets. the amino acid molecules join together in a long chain make a protein molecule. th enumber and sequence of amino acids determines which protein is produced.
What do genes do?
Each protein is made up of a large number of amino acid molecules. since many of the proteins made are enzymes, genes control the cells internal chemistry.
What are genetic causes of variation?
Every sperm and egg cell contains half of the genetic information needed for an individual. Each sex cell is known as haploid, which has half ht enormal number of chromosomes. When chromosomes fuse during fertilisation, a new cell is formed, which is known as a zygote. It has all the genetic information needed for an individual, which is known as diploid and has the full number of chromosomes.
How does inheritance work?
Alleles are different versions of the same gene. For any 2 alleles a person may have the same two alleles known as homozygous or 2 different ones known as heterozygous.
How are alleles either dominant or recessive?
A dominant allele is always expressed, even if only one copy is present (capital letter). A recessive allele is only expressed if the individual has two copies and does not have the dominant allele of that gene (lower case letter).
