Biology: Sexual Reproduction And Meiosis Flashcards
What is sexual reproduction?
Where genetic information from two organisms is combined to produce offspring which are genetically different from their parents
In sexual reproduction, what cells are used to make a child?
Gametes - 23 chromosomes (haploid)
What happens at fertilisation?
Male gamete fuses with female gamete to produce fertilised egg (a zygote) this zygote has a full set of 46 chromosomes (diploid)
What happens to a zygote after fertilisation?
Cell division by mitosis, and it develops into an embryo
What will a embryo inherit from it’s parents?
Characteristics, as it has received a mixture of chromosomes from both
In flowering plants, where are male gametes found and where are female garages found?
Male gametes = pollen
Female gametes = bottom of stigma, in ovaries
How are gametes made?
In meiosis
What makes meiosis different from mitosis?
It doesn’t produce identical cells
Where in humans does meiosis take place?
In the reproductive organs
Give the four steps of division 1 in Meiosis
1) cell duplicates DNA
2) chromosomes line up in pairs in centre of cell. Half of these are from organisms mother, half from father
3) pairs are pulled apart, so each new cell has one copy of each chromosome
4) each new cell will have mixture of mother and fathers chromosomes. Mixing up genes like this creates genetic variation in offspring
Give the two steps of division 2 in Meiosis
1) Chromosomes line up again in the centre of the cell, arms of chromosomes are pulled apart
2) you get four diploid daughter cells, gametes. Each gamete has a single set of chromosome and are genetically different
What are DNA strands? What does this mean?
DNA strands are polymere, meaning they are made up of lots of repeating units joined together
What are the four bases of DNA
Adenine, thymine, cytosine,guanine
What is the structure of one DNA molecule?
Two strands coiled together in the shape of a double helix
How do bases link in DNA?
Each base links to a base in the opposite strand in the helix
What is the complementary base pairings?
A and T
C and G
What are complementary base pairs joined together by?
Weak hydrogen bonds
What’s a gene?
A section of DNA on a chromosome that codes for a particular protein
What is the protein a gene codes for determined by?
The sequence of bases In the gene
What does all of an organisms DNA make up?
It’s genome
Give the four steps of the practical to extract DNA from fruit cells
1) mash some strawberries and put them in a beaker containing a solution of detergent and salt. Mix well. (Detergent breaks down cell membrane, releasing DNA. Salt makes DNA stick together)
2) filter mixture to get forth and Insoluble bits of cell out
3) add ice cold alcohol to filtered mixture
4) DNA will start to come out of solution as it’s not soluble in cold alcohol. Will appear as stringy white precipitate, can be fished out with glass rod
What Are genetic diagrams used for?
To predict how different characteristics will be inherited
What controls what characteristics you develop?
The genes you inherit
What are characteristics controlled by,
Single genes, or several genes interacting
