Inheritance, Variation & Evolution
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What is DNA?
The chemical that makes up all genetic material in a cell and contains coded information for an organism’s characteristics & behaviour
What are chromosomes?
Coils of DNA that usually come in pairs
What shape is DNA?
Double helix
What is a gene?
A small section of DNA within a chromosome
What do genes do?
Code for a particular sequence of amino acids to make up a certain protein
How does DNA determine what type of cell a cell is?
It determines which protein the cell produces/ what job it does
What is a genome?
The entire set of genetic material in an organism
3 reasons discovering the human genome is beneficial?
• Identification of genes related to certain diseases • Effective treatments for hereditary diseases • Migration of earlier populations can be traced
What are DNA strands made of?
Nucleotides
What are the 2 components of a nucleotide?
• Phosphate sugar backbone • Bases
How do the two nucleotides in DNA join?
T and A bases join & C and G bases join
How many pairs of bases code an amino acid?
3
How does code from DNA get to the ribosome for protein synthesis?
mRNA copies code from the DNA and carries the correct amino acids
3 functions of proteins?
• Enzymes • Hormones • Structural proteins
What is a mutation?
A random change in an organism’s DNA which may be inherited
How is mutation chances increased?
Some radiation or substances
2 ways mutations can negatively affect proteins?
• Enzymes’ active sites can be altered so the substrate doesn’t fit • Structural proteins can lose their strength
Why may the function of proteins be affected by mutation?
Mutations change the sequence of bases, leading to a change in amino acids in a protein
What are the 3 types of mutation?
• Insertions - A new base is inserted where it shouldn’t be • Deletions - When a random base is removed from the sequence • Substitutions - When a random base in the sequence is changed to another
What is the offspring of sexual reproduction?
Genetically different (variation in characteristics)
How does sexual reproduction work?
Gametes are produced through meiosis with half the chromosome count of a regular cell - The male and female cells fertilize together and join to create the regular number of chromosomes
What are the offspring of asexual reproduction?
Genetically identical to parents
How does asexual reproduction happen?
Mitosis of an ordinary cell
Explain meiosis in 5 steps.
• Genetic information is duplicated • Chromosome pairs line up down centre of the cell • Pairs are pulled apart so each new cell has one copy of each chromosome • Chromosomes line up again for second division • Arms of the chromosome are pulled apart, resulting in 4 daughter cells each with a single set of chromosomes