Topic 6 - Inheritance, Variation and Evolution Flashcards
Compare sexual and asexual reproduction.
Sexual reproduction:
- – The fusion of male and female gametes.
- – Egg and sperm in animals
- – Egg and pollen in flowering plants
- – Two parents so there is a mix of genetic information which leads to variety in the offspring.
- – Involves meiosis
Asexual reproduction:
- – One parent
- – No fusion of gametes
- – Produces genetically identical offspring (clones)
- – Involves mitosis
What is the process of meiosis?
- – Genetic information is duplicated and then chromosomes arrange themselves in pairs
- – In the first division, chromosomes line up in the centre of the cell
- – Pairs are pulled apart and each new cell has one copy of each chromosome
- – In the second division, chromosomes line up in the centre of the cell again and the arms of the chromosomes are pulled apart by cell fibres
- – Four gametes are produced each with a single set of chromosomes
- – Gametes are all genetically different from each other
What happens after meiosis?
- – Gametes fuse during fertilisation to restore the normal number of chromosomes in a cell (46)
- – The new cell divides by mitosis to replicate itself
- – Mitosis repeats many times to produce lots of many cells in the embryo
- – As the embryo develops, cells differentiate into different specialised cells
What are the advantages and disadvantages of sexual and asexual reproduction?
Sexual reproduction:
- – Variation in offspring
- – If there is a change in environment, the variation increases the survival of the species. This is a survival advantage.
- – More likely to breed successfully and pass the genes for the characteristics on. This is natural selection.
- – Natural selection can be sped up by humans in selective breeding to increase food production.
Asexual reproduction:
- – Requires one parent
- – Less time and energy are used as organisms don’t have to find a mate
- – Faster than sexual reproduction
- – Identical offspring can be produced under favourable conditions
Give three organisms that can reproduce both asexually and sexually.
Malarial parasites:
— Asexually in the human host but sexually in the mosquito.
Fungi:
- – Species of fungus release spores.
- – Asexually-produced spores produce fungi that are genetically identical and sexually-produced spores introduce variation often in response to unfavourable conditions which increase the chance of survival
Plants:
— Seeds can be produced sexually but asexually by runners such as strawberry plants or bulb division such as daffodils.
What does DNA stand for?
Deoxyribonucleic acid
What is the structure of DNA?
- – Polymer made up of repeating units of nucleotides
- – Two strands coiled together to form a double helix structure.
- – Four different bases: A, C, G, T
What is a gene?
Gene:
- – A small section of DNA
- – Each gene codes for a particular sequence of amino acids to make a specific protein.
Define a genome. What is the importance of learning the entire genome?
Genome:
— Entire genetic material of an organism
Importance of learning:
- – Scientists can identify genes linked to diseases
- – Can identify genes linked to inherited disorders which helps to understand them better and develop an effective treatment
- – Can trace human migration patterns from the past
What does each nucleotide consist of?
A phosphate (oval), a sugar (pentagon) and a base (rectangle)
What are the complementary base pairings?
- – A pairs up with T
- – C pairs up with G
How many bases code for a specific amino acid?
3 bases
What is the role of mRNA? Also, what are the complementary pairs between DNA and mRNA?
mRNA acts as a messenger to get the code from the DNA to the ribosome to make protein.
A links to U
T links to A
C links to G
G links to C
What happens after a chain of amino acids has been assembled?
The chain folds into a unique shape to allow the protein to perform its task such as enzymes, keratin, hormones etc.
What are the three different types of mutations?
Insertion:
- – A new base is inserted into the DNA base where it shouldn’t be
- – Changes the way the base is ‘read’
- – Has knock-on effect on bases further down the sequence
Deletion:
- – A new base is deleted from the DNA base
- – Changes the way the base is ‘read’
- – Has knock-on effect on bases further down the sequence
Substitution:
— A random base is changed to another base in the sequence
