Topic 6 - Inheritance, Variation and Evolution Flashcards
What are chromosomes?
Long molecules of DNA
They normally come in pairs
What is DNA?
Deoxyribonucleic acid.
Chemical that all genetic material in a cell is made up from.
Determines what inherited characteristics you will have.
Its a polymer. Made of up two strands coiled together in the shape of a double helix
What is a gene?
A small section of DNA found on a chromosome.
Each gene codes for a particular sequence of amino acids which are put together to make a specific protein. 20 amino acids make a protein.
Genes tell cells in what order to put the amino acids together.
Whats a genome?
A fancy term for the entire set of genetic material in an organism.
What can understanding the human genome help scientists with?
Allows scientists to identify genes in the genome that are linked to different types of disease.
Learning which genes are linked to inherited genes could help develop treatments for them.
Find previous ancestors
What is DNA made of?
DNA strands are polymers made up of lots of repeating units called nucleotides.
Each nucleotide consists of one sugar molecule, one phosphate molecule and one ‘base’.
The sugar and phosphate molecules alternate forming a ‘backbone’. 1 of 4 different bases, (A, T , C OR G) joins to each sugar.
Each base links to a base on the opposite strand.
A always pairs with T and C always pairs with G.
Its the order of bases in a gene that decides the order of amino acids in a protein.
Each amino acid is coded by a sequence of 3 bases in a gene.
Amino acids are joined together to make various proteins, depending on the order of the genes bases.
There are parts of DNA that dont code for proteins. Some of these switch genes on and off so they control whether or not a gene is expressed
How are proteins made?
Made in cell cytoplasm on ribosomes.
Ribosomes use the code in the DNA to make proteins.
Cells get code from DNA to ribosome using a molecule called mRNA - which is made by copying the code from DNA.
What are functions of proteins?
Enzymes - Biological catalysts to speed up chemical reactions.
Hormones - Carry messages around the body.
Structural proteins - Physically strong
What are mutations?
A random change in an organisms DNA.
They occur continuously. Chance could be increased by exposure to certain substances or radiation.
Mutations change the sequence of DNA bases in a gene which produces genetic variant.
Most mutations have little or no effect on protein.
But some can seriously affect a protein. Eg change enzyme active site shape.
What are insertion mutations?
Insertions are where a new base is inserted into the DNA base sequence where it shouldnt be.
Changes the way groups of 3 bases are read which changed the amino acids they code for
What are deletion mutations?
When a random base is deleted from the DNA base sequence.
Change the way a base sequence is read.
What is sexual reproduction?
Sexual reproduction involves the fusion of the male and female gametes. Since there are 2 parents, the offspring contain a mixture of the parents genes
How does the mother and father produce gametes?
Meiosis
In humans how many chromosomes does each gamete have?
23
How do plants reproduce sexually?
They have egg cells which fuse with pollen instead of sperm
