CB3 Genetics Flashcards
Fertilisation
The process where two gametes fuse their dna together to produce a zygote
Meiosis
4 daughter cells made
Cell divides two times
Daughter cells made have 23 chromosomes (haploid)
Cells made are not genetically identical
Advantages of sexual reproduction
Variation in population
Disadvantage of sexual reproduction
Needs to find a mate
Animals who have small population would struggle to find a mate
Advantages of asexual reproduction
Does not need to find a mate
A rapid reproductive cycle
Disadvantage of asexual reproduction
No variation in population
- could all be wiped out by one disease
Differences between meiosis and mitosis - identical and varied
Mitosis - cells are genetically identical
Meiosis - cells are varied
Differences between meiosis and mitosis - daughter cells
Mitosis - 2 diploid
Meiosis - 4 haploid
Differences between meiosis and mitosis - which cells
Mitosis - all normal body cells
Meiosis - sperm and egg cells - gametes
Differences between meiosis and mitosis - what are they needed for?
Mitosis - growth and repair
Meiosis - sexual reproduction
Where is the genetic material found in cells?
The nucleus
Gene
A section of DNA on a chromosome that codes for a particular protein
Allele
A different version of the same gene
What are the complementary bass pairs?
Adenine - thymine
Guanine - cytosine
What is the shape of dna?
Two strands coiled together in the shape of a double helix
What are the complementary base pairs joined together by?
Weak hydrogen bonds
Chromosomes
Long lengths of tightly coiled up DNA. They are found in the nucleus of eukaryotic cells
What is the backbone of dna made out of?
Sugar phosphate backbone
Phenotype
How your characteristics appear, your physical features
Homozygous
Two alleys which are the same
TT tt
Heterozygous
Two alleles that are different
Tt
DNA
The genetic material – a polymer made of sugar and
phosphate groups joined to bases.
Diploid
Cells which contain the full normal number of chromosomes
– 46 in total.
Haploid
Cells which contain half the normal number of chromosomes
– 23 in total.
Zygote
A fertilised egg cell.
Mutation
A mistake in a gene caused by an error in the DNA.
Gamete
Sex cells – sperm and egg.
Genotype
The alleles you inherit from your parents e.g. Aa or GG.
Dominant and recessive alleles
Dominant alleles overrule recessive alleles, so if an organism has a one dominant and one recessive allele the dominant one will determine the characteristic
Mono hybrid inheritance
The inheritance of a single characteristic
What are the male and female alleles?
XY = Male XX= Female
Discontinuous / discrete data
Consists of specific values with nothing in between
Example of discontinuous data
Blood type , earlobes attached or not
Continuous data
Can have any value between two extremes
Example of continuous data
Height, weight and IQ
Normal distribution curve
When we plot a graph of continuous data we often get a particular shape - it shows that most people fall in the middle with fewer individuals at the extremes
Genetic variation
Caused by the DBA found in cells which is unique to each individual as a result of mutation or sexual reproduction
Environmental variation
Acquired characteristics are caused by the influences of the environment an individual is in
Haemoglobin
Allows red blood cells to carry oxygen around the body
Insulin
Picks up glucose in the blood and forces it either into cells for respiration or stores it in the liver on the form of glycogen
Mutation
A change in the sequence of bases in the genetic code
Aims of the human genome project
- To work out the order and sequence of the 3 billion base pairs in the human genome
- to identify all the genes
- to develop faster methods for sequencing dna
Benefits of the human genome
Improved genetic screening
location of genes - might be linked to increased chances of disease
New gene therapy tech
New knowledge of how humans have evolved
Personalised medicines
How are the two strands of dna linked together?
By a series of complementary base pairs joined together by weak hydrogen bonds
Genome
The entire dna of an organism
How do you extract dna from fruit? Method
Mash strawberries - put into beaker with detergent and salt-mix
Filter the mixture to get the frith and insoluble bits of cell out
Add ice cold alcohol to the filtered mixture
The dna should start to come out of solution - not soluble in alcohol
Fish it out with a glass rod
What does the detergent do when extracting the dna?
Breaks down the cell membranes to release the dna
What will the salt do when extracting the dna?
The salt will make the dna stick together
What will the dna look like when extracted?
White stringy precipitate -solid -
Dominant
Capital letter
They overrule recessive alleles
Recessive
Small letter
Both alleles must be recessive to show the recessive characteristic
Gamete
Sperm and egg
Contain only 23 chromosomes- haploid cells
Zygote
Fertilised egg - contains a full set of chromosomes 46- diploid
How is the sex off the offspring determined?
Female - XX
Male- XY
What is genetic variation caused by?
Organisms having different alleles which can lead to differences in phenotype
Can also be caused by new alleles arising through mutations
Sexual reproduction
Mutations effect
Don’t always have a big effects on the phenotype
They can sometime alter an individuals characteristics
Rarely a single mutation can have a large effect on phenotype
