Topic 3a: Genetics (DNA + meiosis) - PAPER ONE Flashcards
What are the advantages and disadvantages of sexual reproduction?
ADVANTAGES:
- Creates genetic variation within the population (different individuals have different characteristics)
- So, if environmental conditions change at least some individuals will have the characteristics to survive
DISADVANTAGES:
- Organisms need to find and attract mates which takes time. This means that the organisms produce fewer offspring in their lifetime
What are the advantages and disadvantages of asexual reproduction?
ADVANTAGES:
- Produces lots of offspring very quickly because the reproductive cycle is fast and they don’t need to find a mate
- So, organisms can colonise a new area very quickly
DISADVANTAGES:
- No genetic variation between offspring.
- So, if the environment changes, the whole population may be affected
- e.g. if there is an outbreak of disease that affects plants that reproduce asexually, the whole population will be affected as none are resistant to it
Explain the role of Meiosis
4 haploid daughter cells are produced and are genetically different from each other (they are Gametes)
Where does meiosis occur in humans?
Reproductive organs
Which cell division occurs for sexual and asexual reproduction?
Sexual - Meiosis
Asexual - Mitosis
Describe the structure of DNA
A polymer made up of…
- Two strands coiled together to form a double helix
- The strands are linked by a series of complementary base pairs
joined together by weak hydrogen bonds
- The sides of DNA are made from alternating sugars and
phosphate molecules (sugar-phosphate backbone)
What are the strands of DNA composed of?
Nucleotides:
a sugar and phosphate group with one of the four different bases attached to the sugar
Which DNA bases link to eachother?
Adenine and Thymine
Cytosine and Guanine
Where are chromosomes found?
In the nucleus of eukaryotic cells
What’s a gene?
A section of a DNA molecule that codes for a specific protein
What’s a genome?
The entire DNA of an organism
Explain how to extract DNA from fruit
CRUSH FRUIT TO CRUSH CELLS AND THEN…
1) Add salt to the water: Causes DNA to clump together
2) Add washing up liquid: Breaks down the cell membranes
4) Add enzyme protease: Breaks down protein in the cell membrane
5) Filter solution to remove the insoluble parts
6) Add ice cold ethanol to filtered mixture: DNA is not soluble in cold alcohol, so it will appear as a white precipitate
The nucleus of a daffodil cell has 46 chromosomes.
State the number of chromosomes in each pollen grain from this daffodil.
23
When the same gene was sequenced in a different person, the sequence went from ATGTAGCC to ATTTAGCC.
Explain why this shows that the gene has more than one allele.
- The sequence is different
- Alleles are different versions of the same gene
The student repeated the experiment.
Give some reasons why.
- Calculate a mean/average
- To see if the results are reliable/the same/correct
- To identify anomalies
- To obtain more data
