Inheritance - Topic 6 Flashcards
What are gametes?
Gametes are a type of cell where chromosomes are not paired.
What are the male and female gametes in humans? How many chromosomes does each contain? What are the male and female gametes in plants?
In Humans, the male gamete is sperm, and the female gamete is an egg cell. They both contain 23 single chromosomes. ‘
In Plants, the male gamete is pollen and the female gametes are egg cells.
What type of cell division is involved in the formation of gametes? What does it produce?
Meiosis, it produces non identical cells.
How does sexual reproduction lead to variety in the offspring? (3 marks)
- Involves the fusion of male and female gametes.
- Two parents, mixing of genetic information.
- When fertilisation occurs, it leads to variation in the offspring.
- Process of meiosis produces this.
What type of cell division occurs in a asexual reproduction?
Mitosis, produces identical cells.
How does asexual reproduction leads to ‘clones’? (3 marks)
Only one parent, does not involve gametes, no mixing of genetic information so identical offspring’s are made, process of mitosis produces this.
How does meiosis produces gametes? How many does it produce?
Stage 1 - All chromosomes are copied.
Stage 2 - Cell divides into two.
Stage 3 - Both of these cells divide one more time, forming gametes. It forms 4 of them.
How many chromosomes does the human cells have before meiosis? How many does it have after?
Before meiosis it has 23 paired chromosomes.
After it has 23 single chromosomes.
How does fertilisation restore the number of chromosomes restore the normal number of chromosomes?
When a male gamete and female gamete fertilise, the cell divides by mitosis forming a clump of cells, called an embryo, the cell now has the normal number of chromosomes.
What are the advantages of sexual reproduction? What are the disadvantages?
Advantages
1. Survival advantage by natural selection.
2. Selective breeding - higher yield.
Disadvantages
1. Mate is required, high energy demand, and more time is needed.
2. Organism must find a mate in order for it to occur.
What are the advantages of asexual reproduction? What are the disadvantages?
Advantages
1. Only one parent needed, more efficient in time and energy so much faster.
2. Useful when conditions are favourable, can produce genetically identical offspring.
Disadvantages
1. Risky, offspring could all die if conditions become unfavourable.
2. If a disease occurs, disease is more likely to affect the whole population as their is no genetic variation.
How, in malaria, do they reproduce by both methods depending on conditions?
In human host, parasite reproduces asexually.
However, in mosquitoes the parasite uses sexual reproduction.
How, in fungi, do they reproduce by both methods depending on conditions?
Fungi reproduce asexually to produce spores.
They can also reproduce sexually for variation in the offspring.
How, in flowering plants, do they reproduce by both methods depending on conditions? (Talk about strawberry plant and daffodils)
All plants reproduce sexually to produce seeds. Plants like a strawberry plant can reproduce asexually to send out runners, when this touches the coil, it can develop genetically identical to the parent.
Daffodils can reproduce asexually by bulb division plant has a bulb underground, which produces buds, they form new identical offspring.
What is DNA? What is the shape formed by a DNA molecule? Where is DNA found?
DNA is genetic material which determines our inherited features.
It consist of two strands, which forms a double helix.
It is found in our chromosomes.
Where is the gene located? What is the function of the gene?
Gene is a small section of DNA located on a chromosome, each gene codes for a different sequence amino acid to make a specific protein.
What is a genome?
The genome is the entire genetic material of an organism.
Why is studying the human genome important?
- It can help us search for a gene that is linked to disease.
- Understand and treat inherited disorders.
- Trace human migration patters from the past (ancestry)
What is the structure of DNA?
It is a polymer of molecules called nucleotides.
DNA consist of 3 ‘shapes’, phosphate group, sugar and a base.
In DNA which two ‘shapes’ never change?
The phosphate group and the sugar.
How many different bases are their? How many different nucleotides?
There are 4 different bases so 4 different nucleotides. The DNA strands are complements so same bases always pair on opposite strands.
What are the complementary base pairings? What are the letters used to represent the four bases in DNA?
The four letters are, C,G,A,T
C is always linked to G.
A is always linked to T.
How many different amino acids are their in humans? What does the specific order of amino acids determine?
There are 20 different amino acids in humans.
The specific order of the amino acids determine the shape of the protein.
The shape of the protein determines it’s functions.
What are the order of amino acids in a protein determined by?
By the sequence of bases in the gene for that protein. The cell reads the DNA sequence as the triplets of bases, each triplet encodes for a specific amino acids in the protein.
