Paper 2: Topic 6 Inheritance, variation & evolution - Reproduction (includes DNA & genetics) (LV) Flashcards
Name the genetic material found in the nucleus
DNA
What does DNA stand for?
Deoxyribonucleic acid
How is the DNA arranged in the nucleus of a eukaryotic cell?
As chromosomes
How is the DNA arranged in a prokaryotic cell?
- Free in the cytoplasm as a nucleoid
- And additional pieces of DNA are also found in bacteria in small loops called plasmids
How do chromosomes normally exist in cells?
In pairs
Where do the chromosomes in the nucleus originate (come) from?
One from each pair comes from the maternal ovum and one from each pair comes from the paternal sperm
What type of molecule is DNA?
Polymer
DNA is a polymer. What are the monomers that are linked other to form DNA called?
Nucleotides
Describe the general shape of a DNA molecule
A double helix
Define the term gene
A small section of DNA that codes for the sequence of amino acids that makes a specific protein
How many amino acids exist naturally?
20
Define the term genome
The entire set of genetic material that exists in a single organism
Why has the study of the Human genome been useful for scientists?
Hint: give 4 reasons
- They have Identified genes linked to specific diseases
- Gained an understanding of how some diseases are inherited
- Used this understanding of inheritance to develop effective treatments
- Used the genome to determine historical migration patterns of certain groups of people
State the 3 main components of a nucleotide
- Phosphate group
- Sugar (called deoxyribose)
- Base
How many different types of base are found within DNA?
4
What are the 4 different types of base found in DNA nucleotides?
A, T, C and G
How do the bases pair up in DNA?
- A always pairs with T
- C always pairs up with G
How do the nucleotide bases code for the production of proteins?
- 3 bases codes for one amino acid
- So the sequence of bases codes for the sequence of amino acids that are linked together to make a protein
Some parts of the DNA do not code for specific proteins. What is the role/function of these parts of the chromosome?
- To control if the genes are expressed
- Which determines if the proteins are actually produced
Which organelle is responsible for producing proteins?
Ribosomes
How are proteins made? Hint: 5 steps
- The instructions in the gene are copied into a messenger molecule called mRNA
- The mRNA leaves the nucleus and travels to the cytoplasm
- Ribosomes attach to the mRNA
- Carrier molecules carry amino acids to the ribosome
- The ribosome joins the amino acids together in the sequence that is determined by the mRNA
After the amino acids are joined together in a long chain, what must happen before the protein can carry out it’s function?
- When the protein chain is complete it folds up to form a unique shape.
- This unique shape enables the proteins to do their function
Give 5 different functions of proteins
Hint: think STEAM H
Structural role e.g. collagen (found in blood vessel walls), keratin (found in hair and nails)
Transport role e.g. haemoglobin (carries oxygen around the body)
Enzymes e.g. proteases
Antibodies
Mechanical role e.g. myosin (found in muscle cells to allow muscle cells to contract)
Hormones e.g. insulin
Define the term mutation
- A change to the sequence of DNA bases
- This changes the genetic code
Describe how often mutations occur
Continuously, spontaneously and randomly
State the 3 effects of mutations
- Neutral
- Harmful
- Beneficial
State 3 factors that increase the risk of a mutation occurring
- Exposure to UV light
- Exposure to X-rays
- Exposure to certain chemicals e.g. benzene
How does a change in DNA bases cause a change in the protein structure and function?
- A change in one or more DNA bases will change the triplet sequence of the DNA
- This will change the sequence of triplets on the mRNA
- This will change the carrier molecule that brings the amino acids to the ribosome
- The sequence of amino acids will then change
- This changes the structure of the protein
- Which then changes the function of the protein
Suggest how mutations may cause a change in enzyme activity
- The mutation will cause the amino acids sequence to change
- This could change the shape of the active site
- This could prevent the substrate from fitting into the active site
- This then prevents the formation of enzyme-substrate complexes
- So the rate of reaction will decrease
Suggest how mutations may cause a change in structural proteins
- The amino acid sequence in the protein will be changed
- This changes the shape of the protein
- This reduces the strength of the structural protein
Describe the function of the non-coding parts of the DNA
- Non-coding parts of DNA can switch genes on and off
- Mutations in these areas of DNA may affect how genes are expressed
Explain why a mutation may not alter gene expression
The mutation may occur in part of the DNA that does not code for a protein
State the 3 different types of mutation
- Insertion
- Deletion
- Substitution
Describe an insertion mutation
- An new additional nucleotide base is inserted into the DNA
- This will alter how the triplets of DNA bases are ‘read’
- Each triplet will change at the point after the insertion
- This is described as a frameshift mutation
Describe a deletion mutation
- A nucleotide base is deleted from the DNA
- This will alter how the triplets of DNA bases are ‘read’
- Each triplet will change at the point after the deletion
- This is described as a frameshift mutation
Describe a substitution
- A nucleotide base in the DNA sequence is changed to a different nucleotide base
- This may alter which amino acid is inserted into the sequence
Name the two types of reproduction
- Asexual reproduction
- Sexual reproduction
Define asexual reproduction
- Asexual reproduction involves only one parent and no fusion of gametes
- There is no mixing of genetic information
- This leads to genetically identical offspring (clones)
- Only mitosis is involved
Define sexual reproduction
- Reproduction that involves two parents
- It involves the mixing of genetic information
- This leads to variety in the offspring
- The formation of gametes involves meiosis
- It involves the fusing of gametes
State the 2 types of gametes that are involved in sexual reproduction in animals
- sperm
- ova (egg cells)
State the 2 types of gametes that are involved in sexual reproduction in flowering plants
- pollen
- ova (egg cells)
Give 3 advantages of sexual reproduction
- Produces variation in the offspring
- If the environment changes variation gives a survival advantage by natural selection
- Natural selection can be sped up by humans in selective breeding to increase food production
Give 4 advantages of asexual reproduction
- Only one parent needed
- More time and energy efficient as do not need to find a mate
- Faster than sexual reproduction
- Many identical offspring can be produced when conditions are favourable