Topic 6a DNA & Reproduction Flashcards
What are chromosomes made up of
Long molecules of coiled up DNA
Why are DNA molecules described as double helix
Because they are made up of two strands coiled up together in the shape of a double helix
How does a gene help to make a specific protein
It tells the cells in what order to put together the amino acids in order to make a specific protein.
Define the word Genome
A Genome is the entire set of genetic material in an organism
Why is understanding the human Genome important for science and medicine
- It allows scientists to identify genes in the Genomes that are linked to specific diseases
What is a nucleotide made of
One sugar molecule, One Phosphate molecule (Sugar and Phosphate Backbone) and one base pair AT, CG,
Which part of the nucleotide alternate to from a DNA Strand
Sugar and Phosphate molecules alternate e.g. sugar, phosphate, sugar, phosphate
How many bases code for an amino acid
3 bases e.g. Asparagine = AAT
How does the sequence of bases in a gene control which particular protein is made
Each sequence of three bases is coded to a specific amino acid. These amino acids are joined together to form a particular protein depending on the order of the bases e.g. TCT codes for Serine
Bases code for amino - amino form particular protein
In what order are the components of a nucleotide joined together
Base is always attached to the sugar and the the sugar attaches to the a phosphate
Where are proteins assembled
Proteins are made in the cell cytoplasm on tiny structures called ribosomes
What is the role of mRNA
mRNA is a copy of the DNA code for protein taken from the nucleus and moved to the ribosomes where protein is then synthesised
MRNA - copy of DNA code for protien - moved form nucleus - to ribosomes (for synthesis)
How many different amino acids are there in humans
20
What are carrier molecules and what do they do
They bring amino acids to the ribosomes in the correct order in order to assemble and form a unique shape (A Protein to perform a specific task) i.e Enzymes, Hormones, Structural Proteins
What happens when a protein chain is complete
It forms a unique shape to perform a specific task
- Enzymes = Biological catalyst to speed up chemical reactions
- Structural Protein = a physically strong structure like collagen which strengthens connective tissue
- Hormones = Used to carry messages around the body e.g. insulin to regulate blood glucose levels
Form unique shape - for specific function - enzyme/hormone/ structural protein
What is a mutation in genes and how does is occur
A mutation is a random change in an organisms DNA
It occurs when a gene isn’t quite replicated properly changing the sequence of DNA bases in a gene
How do mutations affect proteins
Mutations can sometimes lead to changes in proteins as mutations change the sequence of DNA Bases in a gene. These bases code for the sequence of amino acids that make up proteins. Mutations can alter the proteins shape affecting enzyme substrates ability to bind to its active site as the shape of the site has changed.
Mutation changes base sequence in gene leading to changes in protein - alter shape of protein - substrate cant fit active site
True or false Mutations occur continuously
True
What are insertions in regards to Mutation
Change in base sequence - which changes the amino acid the 3 bases code for
An insertion refers to a change in the DNA base sequence where it shouldn’t be. It changes the way the groups of the three base pairs are read which in turn changes the amino acid they code for.
(EXTRA LETTER INSERTED) e.g -
Origional gene = TAT/AGT/CTT
Insertion = TAT/AGG/TCT/T insertion has caused for a different amino acid to be coded for
What are Deletions in regards to mutations
Deletions are when a random base is deleted from the DNA Base sequence. Like insertions they alter the way that the base sequence is read and have a knock on effect further down the sequence.
What are substitutions in regards to mutations
Substitutions are when a random base in the DNA base sequence is changed to a different base
What is the difference between Sexual Reproduction and Asexual reproduction
Sexual Reproduction = Genetic information from 2 organisms is combined to produce offspring which are genetically different to either parent
ASexual Reproduction = Only one parent so offspring are genetically identical to the parent. No fusion of gametes, no mixing of chromosomes.
What are Gametes
Gametes are reproductive/sex cells which unite during sexual reproduction.
What is fertilisation
Fertilisation is the fusion of Gametes. In humans Male sperm fuses with female egg to form a cell with the full number of chromosomes half from the father and half from the mother.
Fusion of Gametes - form a cell - full no of chromosomes - Half Male Half Female
Are Gametes produced by Meiosis or Mitosis
Meiosis = two divisions
How are Gametes produced
Gametes are produced by meiosis. They only have 1 copy of each chromosome so that when gamete fusion takes place the right amount of chromosomes are present (two copies from each gamete)
To make gametes with only have half the amount of the original number of chromosomes the meiosis process involves two cell divisions.
How many sets of chromosomes do gametes have
one
Where are gametes produced
Reproductive organs
How many new cells are produced when a cell divides by meiosis
4
Following fertilisation, how does the resulting cell grow
By repeatedly dividing by Mitosis
Advantages of Sexual reprodution
- Offspring have genetic information from both parents so there is a mixture of genetic information.
- This produces variety which increase the chance of a species surviving a change in environment.
- the species can adapt to new environments due to variation, which gives them a survival advantage.
- a disease is less likely to affect all the individuals in a population.
Disadvantages to Sexual Reproduction
The disadvantages of sexual reproduction:
- time and energy are needed to find a mate
- it is not possible for an isolated individual to reproduce
Advantages to Asexual reproduction
- the population can increase rapidly when the conditions are favourable
- only one parent is needed
- it is more time and energy efficient as you don’t need a mate
- it is faster than sexual reproduction
Disadvantages to Asexual reproduction
- it does not lead to genetic variation in a population
- the species may only be suited to one habitat
- disease may affect all the individuals in a population
When does the Malaria parasite reproduce Asexually
It produces Asexually when its in the human host
Explain how a strawberry plant reproduces Asexually
It produces runners, these are stems that grow horizontally on the surface of the soil away from the plant. At various points along the runner a new strawberry plant will form which is identical to the original plant.
