Flashcards in T3 - Genetics Deck (52):
Where genetic information from 2 organisms is combined to produce offspring which are genetically different to both parents
Cells which contain half the number of chromosomes (sperm and egg has 23)
What happens at fertilisation? (in animals)
Male gamete rises with female gamete to produce zygote which is diploid
Zygote which has grown by mitosis
How is meiosis different to mitosis?
Meiosis doesn’t produce identical cells
Describe what happens in meiosis first division after the DNA has been duplicated
Chromosomes line up in pairs in the centre of cell (1 chromosome from mother, 1 from father)
Pairs are pulled apart
Each new cell has a mixture of father and mother chromosomes
Describe what happens in meiosis second division
Chromosomes line up again in the centre of cell
Arms are pulled apart
4 haploid daughter cells (gametes) each gamete only has a single set of chromosomes
Advantages of asexual reproduction (2)
Produce many offspring quickly
Only one parent is needed
Disadvantages of asexual reproduction (2)
No genetic variation
So, if environments change, the whole population may be affected
Advantages of sexual reproduction (3)
Creates genetic variation
So, if environments change, more likely that some of the population will survive
Over time, can lead to evolution and natural selection
Disadvantages of sexual reproduction (3)
Takes time and energy
So, fewer offspring are made
2 parents are needed
Strands of polymers made up of lots of repeating units called nucleotides
Each nucleotide consists of....
One sugar molecule, one phosphate molecule and one ‘base’
‘Backbone’ to DNA strands
Formed by sugar and phosphate molecules in the nucleotides that alternate
Bases join to....
A (adenine), T (thymine), C (cytosine), G (guanine)
Double stranded spiral, shape of DNA molecule
Each base links to....
A base on the opposite side of the helix
Complementary base pairing
A pairs with T, C pairs with G
What are the complementary base pairs joined together by?
Weak hydrogen bonds
Section of DNA on a chromosome that codes for a particular protein
All of an organism’s DNA (including non-coding)
Each amino acid is coded for by a sequence of 3 bases in the gene
Some DNA doesn’t code for any amino acids
Rare, random change to an organism’s DNA base sequence that can be inherited
A different version of the gene (if mutation happens in the gene)
Where are proteins made?
In the cell cytoplasm, made by ribosomes
Messenger RNA (mRNA)
Polymer of nucleotides but it’s shorter and only a single strand. Used to get the information from the DNA in the nucleus to the ribosome in the cytoplasm
mRNA uses.... instead of.... as a base
U (uracil), T (thymine)
Enzyme involved in joining together RNA nucleotides to make mRNA
What happens in transcription (first stage of protein synthesis)
RNA polymerase binds to a region of non-coding DNA in front of a gene
2 DNA strands unzip, RNA polymerase moves along 1 DNA strand
Uses coding DNA in the gene as a template to make mRNA (base pairing between DNA and RNA ensures mRNA is complementary to the gene)
Once made, mRNA moves out of nucleus and joins with a ribosome
What happens in translation (second stage of protein synthesis)
Amino acids are brought to the ribosomes by transfer RNA (tRNA)
The order in which the amino acids are brought to the ribosomes matches the order of the codons
The pairing of the anticodon and codon makes sure the amino acids are brought to the ribosome in the correct order
Amino acids are joined together by the ribosome (makes polypeptide (protein))
Base triplets in mRNA are also known as....
Part of the tRNA’s structure - complementary to the codon for amino acids
Sex-linked genetic disorders
Disorders caused by faulty alleles located on sex chromosomes
4 potential blood types
O, A, B and AB
The gene for blood type in humans has 3 different alleles, what are they?
I^O , I^A , I^B
One allele isn’t dominant over the other
What blood type would I^A and I^B produce?
What blood type would I^O and I^A produce and why?
A, because I^O is recessive so you only see the effect of I^A
What’s the genotype for blood type O?
What was the idea behind the human genome project?
To find every single human genome (20,500)
What characteristics you have - determined by your alleles
When did the human genome project start and finish?
1900 ended in 2003
How many genes found are related to disease?
How can genes prevent common diseases such as cancer and heart disease?
With the right lifestyle, we could avoid them because they’re caused by the interaction of different genes
How has the human genome project helped in the treatment and testing for inherited disorders (eg cystic fibrosis)?
Caused by faulty alleles in a person’s genome. Now, scientists can identify the genes and alleles that are suspected of causing an inherited disorder. People can be tested for it and develop better treatments
Drawbacks of the genome project
Increased stress - if someone knows they’re susceptible to a disease they could panic (placebo effect)
Gene-ism - people could be under pressure to not have children
Discrimination by employers and insurers - expensive life insurance and employers might discriminate against people who are likely to get a disease
Austrian monk who trained in maths and natural history. Noticed (in 19th century) that characteristics were passed on in plants through generations