Topic 6-Inheritance, Variation and Evolution Flashcards
What is sexual reproduction?
It involves the joining of male and female gametes, each containing genetic information from the mother or father
A gamete from each parent fuses to form a zygote and genetic information from each gamete is mixed so the resulting zygote is unique
What are gametes?
Sex cells (sperm and egg cells in animals, pollen and egg cells in flowering plants)
Haploid (half the number of chromosomes)
How many chromosomes does a normal cell have?
46
What is asexual reproduction?
Involves only one parent (no gametes joining)
Happens only using the process of mitosis
No genetic variation and leads to clones (genetically identical to each other and the parent)
eg bacteria, some plants and some animals
What must occur prior to meiosis?
Interphase-copies of genetic information are made during this process
What happens during the first stage of meiosis?
Chromosome pairs line up along the cell equator
The pair of chromosomes are separated and move to opposite poles of the cell (the side to which each chromosome is pulled is random, creating variation)
Chromosome number is halved
What happens during the second stage of meiosis?
Chromosomes line up along the cell equator
The chromatids are separated and move to opposite poles of the cell
Four unique haploid gametes are produced
Why is meiosis important for sexual reproduction?
It increases genetic variation
It ensures that the zygote formed at fertilisation is diploid
Describe fertilisation and its resulting outcome
Gametes join at fertilisation to produce a cell with 46 chromosomes, the normal number
This cell divides by mitosis to produce many copies
More and more cells are produced and an embryo forms
The cells begin to take on different roles after this stage (differentitation)
What does the term haploid mean?
When the nuclei only contain one set of chromosomes each
What does the term diploid mean?
When the nuclei contain two sets of chromosomes
What does DNA stand for?
Deoxyribonucleic acid
What is DNA?
A double-stranded polymer of nucleotides, wound to form a double helix
The genetic material of the cell in found in its nucleus
What is each nucleotide made up of?
One sugar molecule, one phosphate molecule (forms backbone) and one of the four types of organic bases
Define genome
The entire genetic material of an organism
What are the four types of organic bases?
A, C, G, T
Why is understanding the human genome important?
The whole human genome has been studied and is important for the development of medicine in the future
-Searching for genes linked to different types of disease
- Understanding and treating inherited disorders
- Tracing human migration patterns from the past
What is a chromosome?
A long, coiled molecule of DNA that carries genetic information in the form of genes
Define gene
A small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
Describe how nucleotides interact to form a molecule of DNA
Sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand
Base connected to each sugar
Complementary base pairs (A pairs with T, C pairs with G) joined by weak hydrogen bonds
Explain how a gene codes for a protein
A sequence of three bases in a gene forms a triplet
Each triplet codes for an amino acid
The order of amino acids determines the structure and function of protein formed
Describe the process of meiosis
The cell makes copies of its chromosomes, so it has double the amount of genetic information
The cell divides into two cells, each with half the amount of chromosomes (46)
The cell divides again producing four cells, each with a quarter the amount of chromosomes (23)
These cells are called gametes and they are all genetically different from each other because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells
Why is the ‘folding’ of amino acids important in proteins such as enzymes?
The folding of amino acids determines the shape of the active site which must be highly specific to the shape of its substrate
What is protein synthesis?
The formation of a protein from a gene