Topic 3 - Genetics Flashcards
What is sexual reproduction
Genetic information from two organisms ( a father and mother ) is combined to produce offspring genetically different to either parent
In sexual reproduction the parent produce gametes. In Animals this is sperm and egg cells
Gametes
The reproductive cells of a plant or animal. These are HAPLOID ( only 1 set of chromosomes )
Zygote
At fertilisation, the male gamete fuses with the female gamete to produce a ferilised egg called a ZYGOTE. This has the full set of chromosomes - DIPLOID
How does a zygote develop into an embryo?
It undergoes cell division by mitosis.
This embryo inherits characteristics from both parents, as it has recieved a mixture of chromosomes
How are gametes produced?
By meiosis
Meiosis vs mitosis
Mitosis produces clones. - Diploid
Meiosis doesnt produce identical cells - Haploid
Where does meiosis happen in the body?
In the reproductive organs
How does the FIRST DIVISION of meiosis
- before the cell divides, it duplicates its DNA
- The chromosoes line up in pairs at the centre of the cell - one of the pair from the organisms mum, one from their dad
- The pairs are then pulled apart, so each one only has 1 copy of each chromosome - some of the mum nad some of the dads chromosomes go into each cell
Each new cell with have a mixture of the mothers and the fathers chromos
Creates Genetic variation
How does the SECOND DIVISION of meiosis
- The chromosomes line up in the centre again, but ovbi not in pairs dun
- The chromatids of the chromosomes are pulled apart
- This creates 4 Haploid daughter cells - these are the Gametes
The gametes are all genetically different
What are the ADVANTAGES of ASEXUAL reproduction
- can produce lots of offspring very quickly - This allows organisms to colonise a new area very quickly
-One parent is needed - Organisms can produce whenever conditions are favourable, without having to wait for a mate
What are the DISADVANTAGES of ASEXUAL reproduction
- there is no genetic variation in the population
- ## Suceptable to environment changes, they cannot adapt
What are the ADVANTAGES of SEXUAL reproduction
- Creates Genetic variation
- Not suceptable to environment changes - adaptability
- Natural selection and evolution makes these always better suited to their environment conditions
What are the DISADVANTAGES of SEXUAL reproduction
- Takes more time and energy than Asexual reproduction, organisms produce less offspring in their life
- Two parents are needed, a problem is an organism is isolated.
What is a DNA strand made of?
Dna is a polymer made up of Nucleotides
What does each nucleotide in a DNA consist of?
A sugar, a phosphate group and one base
What do the Sugar and phosphate group form in DNA?
The strands, the sugar and phosphate group alternate
Where are the bases in DNA and what 4 bases are there?
The bases join to the sugars
Adenine - Thymine
Cytosine - Guanine