Topic 3 - Genetics Flashcards
Sexual reproduction produces genetically identical cells. True or false?
False - sexual reproduction produces genetically different cells
Name the gametes in humans?
Sperm and egg cells
What are gametes?
Sex cells
What happens to the DNA in a cell before the first division in meiosis?
It duplicates it’s DNA so that there is one copy for each new cell
Why is reproducing important?
It is important because this is how they pass on their genes to the next generation
What are advantages of asexual reproduction? Name 3
1) You don’t need to find a mate
2) You can produce offspring very quickly
3) Organisms can reproduce whenever conditions are favourable
Give a reason why sexual reproduction can take more time than asexual reproduction
With sexual reproduction, you will need to wait to find a mate, whereas with asexual reproduction, this process can start immediately
What is meant by the term ‘double helix’?
It is the shape of DNA
When extracting DNA from a fruit, what is the purpose of mixing the fruit with detergent?
The cell membranes will be broken down to release the DNA
What effect does ice-cold alcohol have on a solution containing free DNA molecules?
It makes the DNA come out of the solution as it is not soluble in the cold alcohol. It will appear as a stringy white precipitate (a solid) that can be carefully fished out with a glass rod
Proteins are made up of _____ _____ joined together in a long chain
Amino acids
How do DNA bases code for specific amino acids?
The different codons (3 bases) will be read during translation. There are round 20 different amino acids that can be made. Each codon tells the ribosome to product an amino acid. When finished, there will be a long chain of amino acids, which make up a specific protein
Name the enzyme that joins together RNA nucleotides to make mRNA
RNA polymerase
How can a mutation in non-coding DNA affect the phenotype of an organism?
It will affect how much mRNA is transcribed and therefore how much of the protein is produced. And, depending on the function of the protein, the phenotype of the organism may be affected by how much is made
What is a nucleotide?
Strands of polymers made up of lots of repeating units ca
What does each nucleotide consist of?
One sugar molecule, one phosphate molecule and one base
What are the four different bases, and which ones pair up with which?
A, T, C, G
A &T
C & G
What is complimentary base pairing?
Where two bases pair up correctly. For example, A always pairs up with T, and C always pairs up with G
What are the complementary base pairs joined together by?
Weak hydrogen bonds
What are chromosomes?
Long, coiled up molecules of DNA. They are found in the nucleus of eukaryotic cells
What is a gene?
A section of DNA on a chromosome that codes for a particular protein
All of an organism’s DNA make up its ______
Genome
What is the process of transcription?
1) RNA polymerase binds to the region of non-coding DNA in front of a gene
2) The two DNA strands unzip and the RNA polymerase moves along one of the strands of DNA
3) It uses the coding DNA in the gene as a template to make sure the mRNA. Base pairing between the DNA and RNA ensures that the mRNA is complementary to the gene
4) Once made, the mRNA molecule moves out of the nucleus and joins with the ribosome
What is the process of translation?
1) Amino acids are brought to the ribosome by another RNA molecule called tRNA
2) The order in which the amino acids are brought to the ribosome matches the order of the base triplets in mRNA. Base triplets in mRNA are also known as codons
3) Part of tRNA’s structure is called an anticodon - it is complementary to the codon for the amino acid. The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order
4) The amino acids are joined together by the ribosome. This makes a polypeptide (protein)
What is a polypeptide?
The chain of amino acids that are joined together by the ribosome.
What experiment did Mendel carry out?
He carried out an experiment with pea plants on how characteristics in plants were passed on from one generation to the next (height)
What were the processes involved in Mendel’s pea plant experiment?
1) In one experiment, Mendel crossed two pea plants of different heights - a tall pea plant and a dwarf pea plant. The offspring produced were all tall pea plants
2) He then bred together two of these tall offspring together. He found that when the offspring from the first cross were crossed with each other, three tall offspring were produced for every one dwarf offspring overall. In other words, he produced a 3 : 1 ratio of tall : dwarf plants
From Mendel’s ratio of 3 : 1 of the tall : dwarf pea plants, what does this tell us about dominant and recessive genes?
The ‘T’ (tall) gene was the dominant gene as it was expressed more often than the ‘t’ (dwarf) gene that was clearly the recessive gene
Give the three conclusions that Mendel reached from his experiment
1) Characteristics in plants are determined by “hereditary units”
2) Hereditary units are passed on to offspring unchanged from both parents, one unit from each parent
3) Hereditary units can be dominant or recessive - if an individual has both the dominant and the recessive unit for a characteristic, the dominant characteristic will be expressed
What does homozygous mean?
An organism has two of the same allele - e.g both dominant or both recessive
What does heterozygous mean?
An organism has two different alleles - one dominant and one recessive
What is monohybrid inheritance?
A cross between two parents who possess different alleles
A couple have a child.
What is the probability that the child will have the XX combination of sex chromosomes?
50/50 or 50% chance
How are carriers shown on a family pedigree
They will have a recessive gene shown. They are not a sufferer because they have a dominant allele
What type of cell division produces gametes?
Meiosis
Why are there more genes on an X chromosome than a Y chromosome?
The Y chromosome is smaller than the X chromosome, and will therefore carry fewer genes
Colour blindness is a sex-linked disorder. True or false?
True
Why are men more likely to be colourblind than women?
Because the Y chromosome doesn’t have an allele for colour vision. Men only need one copy of the recessive gene to be colourblind, whereas women need two
What is the name given to a person with only one copy of a recessive allele for a genetic disorder?
A carrier
What is meant by the term “co-dominance”?
Sometimes you get more than two alleles for a single gene. For example, humans have four potential blood types (O, A, B, AB). The gene for blood type has three different alleles - IO IA and IB - (O, A, B are small letters)
IA and IB are co-dominant with each other because if an individual had both of these alleles, then they would have the blood type AB
What blood group is recessive?
O - you only get O blood with having two recessive alleles
What blood group does an individual have if they have the genotype IA IO?
A - because A is a dominant allele and O is a recessive allele, it means A takes priority, making the blood type A
What causes genetic variation in species?
Organisms having different alleles which can lead to differences in phenotype (the characteristics the organism displays)
What is an acquired characteristic?
They are characteristics that organisms acquire (get) during their lifetime
Name a genetic mutation that affects the phenotype
Cystic fibrosis
Name 2 symptoms of cystic fibrosis
1) Excess mucus in the lungs and digestive system
2) Difficulty breathing or swallowing
What is the Human Genome Project?
A project that maps all of the genes known. So far, they have managed to map over 20,000 genes, 1,800 of which are genes related to disease which will have huge benefits to medicine
Name 3 medical applications for the Human Genome Project’s research
1) Prediction and prevention of disease
2) Testing and treatment for inherited disorders
3) New and better medicines
Describe 3 potential drawbacks / disadvantages of being able to read a person’s genome
1) Increased stress - If someone at a young age knew a risk for a nasty disease, they could panic even if they might never get the disease
2) Gene-ism - people with genetic problems could be put off having children
3) Discrimination by employers and insurers - life insurance could become impossible to get, or expensive at least if you at risk of a serious disease. Employers may discriminate against people who are likely to get a genetical disease
