B6 Genetics Flashcards
Genome
The entire genetic material of that organism
Chromosomes
The DNA is found within structures
Gene
A short section of DNA that contains the instruction for one characteristics of an organism
DNA genes and chromosomes
Human cells have 46 chromosomes
DNA has proteins associated with it that help condense into chromosomes
Mitochondria contain DNA
Plasmids contain DNA but don’t contribute to the running of the cell
Gene therapy and genome edititing
Developing effective treatments to target and correct genes
Understanding someone’s genome may allow doctors to:
Recommend better preventative medicine
Identify the targets of drugs more effectively
Tailor healthcare to the individual
Understanding more about the human genome
In late 20th C it was estimated that there were around 1000000 genes in the human genome
There are much less however 20000-25000 code for proteins this around 1.5% of the human genome
There are no coding areas which control gene expression turning on and off genes
The Genographic project
Looks at characterises on the male Y chromosomes and DNA in mitochondria from women
What were the findings of the TGP
That people originated from Africa
And that they migrated 60000 years ago through Arabia
Structure of DNA
A double helix structure
Like a gently twisted ladder
Bases in DNA
Adenine A
Thymine T
Cytosine C
Guanine G
DNA is a polymer
Made up of repeating units call nucleotides
Genetic code
Is the bases that make up this
Our genome contains approximately 3.3billion base pairs
Genes vary in size from a few hundred bases for more than 2 million
Complementary base pairs
A&T
C&G
Genes are needed to assemble proteins
Genes provide code for assembly of proteins
All proteins made up of same 20 amino acids
4 base pairs work in triplets for each amino acid
Protein synthesis
DNA unzips the bases of a gene act as template for a messenger molecule
Messenger molecule leaves the nucleus containing the code for the amino acid
In the cytoplasm the messenger molecules attaches to a ribosome
The base pairs are complementary. The carrier attaches to the ribosome
A second amino acid is ferried to the ribosome
The second amino acid is able to attach because of the sequence of its bases
A peptide bond is formed between the two anime acids
The messenger molecule is shunted along the ribosome and another amino acid is ferried in
The shape of proteins
Proteins bend into unique shapes creating an active site
When a complementary substrate fits into its active site a reaction can occur
Mutations
Changes to our DNA
Usually to help a species survive
Mutations to amino acids
Some changes may not directly affect the function of an amino acid
If it occurs in a non coding area a gene may be expressed differently
Mutations can have serious side effects
A change in bases to code for a protein may result in a different protein being produced
Therefore the active site is different and specific chemical reactions can not occur
During meiosis
4 gametes are produced from one parent
Each gamete has half the number of chromosomes of the parent cell
What happens during meiosis
There is 2 sets of division
The DNA is copied and then split
Genetic variation
Each gamete receives different characteristics
What determines our sex
Wether we receive X or Y chromosomes determines wether we are male or female
Asexual reproduction
Involves only one parent Offspring are clones of parents Good if can't find a partner Produces lots of offspring quickly in favourable conditions Requires less energy
Sexual reproduction
Genetic material comes from both parent
Produces variation
If environment changes some offspring are more likely to survive than others through natural selection
Using both forms of reproduction
Some species can use either form to reproduce making their survival greater
Adapting to circumstances
Sexual reproduction helps increase the chance of survival
Cystic fibrosis
Is an inherited disorder
Thick sticky mucus makes it hard to breathe
Linked to chromosome 7
Occurs when alleles of CFTR are defective
Dominant or recessive
Dominant only need one allele of it
Recessive needs two alleles for it to be inherited
Genotype
Alleles present for a particular gene
Phenotype
How the gene is expressed
Physical appearance of characteristics eg eye colour
Homozygous
Having 2 of the same allele either recessive or dominant
Heterozygous
2 different alleles both recessive and dominant
Punnet square
Shows all the possible outcomes of the children based on the parents alleles
Gene disorders
Generally caused by recessive alleles
Although some can be dominant
Family tree diagrams
Allows us to see how the condition is passed down in the family
Embryo screening
Embryos can be screened for genetic disorders
If one if found it is up to the parents to decide whether to keep it or not
Gregor Mendel
Was a Monk at a monastery in Bünn now Brno in the Czech Republic
Why did Mendel choose peas
A wide variety available Each trait was sharply defined Fertilisation can be controlled Easy to cultivate They grow and flower He started with pure lines for 2 years
Mendels hypothesis
Inheritance of each characteristic was in units which were passed to descendants
Each plant has a pair of factors governing a particular characteristic
One of these factors at random would go into a gamete
How did he test his hypothesis
Used colour seed trait test
Cross bred 2 colours
Predicted 1:1 ratio
But ended up with 58 yellow and 52 green
Reproducibility of Mendels experiment
Very reproducible as many other scientists have done it and received similar results
