P1B3 - Genetics Flashcards
What is meiosis?
Cell division of four genetically non-identical daughter cells.
Meiosis is used in sexual reproduction.
Process of meiosis?
During meiosis, each pair of chromosomes replicate and the cell splits in two.
There are now two identical cells.
The diploid cell divides again.
Cells split
This creates four genetically different gametes that each have half the number of chromosomes of the parent cell.
Once the gametes fuse, the new cell divides by mitosis.
As soon as the embryo reaches a certain size, cells begin to differentiate (specialise).
Features of asexual reproduction?
No gamete fusion
1 parent
Offspring are clones
Cells divide by mitosis
Advantages of asexual reproduction?
No mate required
Identical offspring
Faster
Advantages of sexual reproduction?
Variation in offspring
Humans can speed up artificial selection through selective breeding of plants and animals.
What is DNA?
Dna is made up of polymers coiled up to form a double helix
What is a gene?
A small section of DNA.
What do genes do?
Genes code for a sequence of amino acids, which combine to give a specific protein.
What are chromosomes?
Long strands of DNA are coiled up to form chromosomes.
Chromosomes contain many genes.
How many chromosomes does a human body cell contain?
46
23 pairs
What is a genome?
The genome is the entire (all) genetic material of an organism.
DNA extraction practical steps?
Grind a sample of strawberry in soapy water
This breaks open cells, releasing the DNA from within cells.
Filter the sample
Very slowly, pour ice-cold ethanol into the filtrate.
The DNA moves into the ethanol by precipitation, and can then be removed with a wire loop.
In what year was the Human Genome Project?
2003
What did we understand about the HGP project for future benefits?
Gene identification
Personalised medicine
Gene therapy
Improved understanding of inherited diseases
Early diagnosis
What’s an allele?
Different variations of the same gene.
eg. blue eyes, brown eyes.
(Gene IS the eye colour.)
What is the genotype? What is the phenotype?
Genotype - The allele combination code - eg. BB Bb
Phenotype - The characteristic expressed due to the genotype - eg. XX is for FEMALE. Female is the phenotype.
What does hereditary mean?
If a characteristic or disease/illness can be inherited.
What is a mutation?
A change in a gene that creates a new allele
How can a mutation cause variation?
Mutations mostly take place during cell division when a mistake is made copying a DNA.
A change in the DNA base sequence COULD change the amino acid sequence which COULD change the protein synthesis in the ribosomes.
What is a protein?
Polymers made from a long chain of amino acid monomers
What is mRNA?
Messenger RNA
Why can’t DNA leave the nucelus? What happens instead?
DNA is too large of a molecule.
Instead the base sequence is sent to the ribosomes using mRNA.
What are the 2 stages of protein synthesis?
Transcription (nucleus) - Forms short mRNA strand (U)
mRNA exits nucleus and travels to ribosomes
Translation (ribosomes) - Forms a polypeptide chain
What happens during transcription?
An enzyme (RNA) Attaches to DNA strand right before the targeted gene base sequence
The enzyme unzips the DNA strand and moves along the DNA template
Enzyme then adds complimentary RNA nucleotides and are attached together to form a strand of mRNA. (T’s are replaced with U’S in mRNA)
