Genetics Flashcards
What are the advantages of sexual reproduction?
- Produces variation in offspring as they are genetically different
- The species can adapt to different environments, survival advantage
- Prevents extinction of the species
What is the disadvantage of sexual reproduction?
Organism must find a mate which requires time and energy
What are the advantages of asexual reproduction?
- Population can increase rapidly if conditions are favourable
- Only one parent is needed
- More time and energy efficient
What is the disadvantage of asexual reproduction?
- Offspring are genetically identical so there is no variation
- If the environment changes all may die
What is sexual reproduction?
- Gamete from mother fuses with gamete from father
- Mixes genetic information from each parent
- Offspring have different combinations of genes
What does meiosis produce?
- Four daughter cells each with half the number of chromosomes
- Genetically different haploid gametes
How can you extract DNA from fruit?
- Grind kiwi up with pestle and mortar
- Mix salt (to make the DNA stick together) and washing up liquid (to break down the cell and nuclear membrane) into the kiwi
- Heat the mixture at about 60° for 5 minutes
- Filter the mixture to get the filtrate
- Cool using an ice bath and gently pour chilled ethanol (to make the DNA precipitate) on top of the filtrate
- Observe the precipitate at the top of the tube
How do genes code for proteins?
- Each triplet of bases codes for one particular amino acid
- The amino acid molecules join together in long chain to form a protein molecule (often enzymes)
- The number and sequence of amino acids determines which protein is produced
What are the stages of transcription?
- The DNA helix is unzipped by the enzyme RNA polymerase breaking the weak hydrogen bonds between base pairs
- RNA polymerase binds to a non-coding DNA just before the gene
- RNA polymerase moves along the DNA strand
- Free RNA nucleotides form hydrogen bonds with the exposed DNA strand nucleotides by complimentary base pairs forming a strand of mRNA
- T is replaced with U in RNA nucleotides
- This happens in the nucleus and when completed will travel to the ribosome
What are the stages of translation?
- The mRNA strand travels through cytoplasm and attaches to ribosome
- For every 3 mRNA bases, the ribosome lines up one complimentary molecule of tRNA (codon)
- tRNA molecules transport specific amino acids to the ribosome
- Used tRNA molecules exit and collect another specific amino acid
- The chain of amino acids in the correct order is called a polypeptide
What is a phenotype?
Visible characteristics of an organism which occur as a result of its genes
How does a genetic variant affect coding DNA?
- Will alter the sequence of bases
- Therefore will change the sequence of amino acids
- This alters the final structure of the protein produced
How does a genetic variant affect non-coding DNA?
- The enzyme RNA polymerase binds to non-coding DNA
- So a change in the order of bases can affect the amount of RNA polymerase that can bind to it
- If less RNA polymerase can bind, less mRNA can be formed and the structure of the final protein is affected
What conclusions did Gregor Mendel come to?
- Offspring inherit ‘hereditary units’ from each parent
- One unit is received from each parent
- Units can be dominant or recessive and cannot be mixed together
What is a gamete?
An organism’s reproductive cell which has half the number of chromosomes (23)
