Reproduction (Edexcel GCSE Combined Science: Biology): Flashcards
Exam code: 1SC0
1/220Still learning
Know0
- FrontThe Role of Meiosis
Meiosis
Was this flashcard helpful?
Cards in this collection (22)
Meiosis
A type of cell division in the reproductive organs that produces genetically different haploid gametes. The chromosome number is halved from diploid to haploid, so it is a reduction division.
Gamete
A sex cell (e.g. sperm and egg cells in animals, or pollen grains and ovum cells in plants), produced by meiosis.
Haploid
Having half the normal number of chromosomes.
Where in the body does meiosis take place?
In the reproductive organs.
Why must the chromosome number be halved when gametes are formed?
Otherwise, when the gametes join at fertilisation to form the zygote, there would be double the number of chromosomes.
How many daughter cells does meiosis produce, and how many chromosomes does each contain?
Four haploid daughter cells, each with half the number of chromosomes.
Why is meiosis described as a reduction division?
Because it halves the chromosome number, from diploid to haploid.
How does meiosis increase the genetic variation of offspring?
It forms new combinations of maternal and paternal chromosomes each time a gamete is made, so when gametes fuse randomly at fertilisation, each offspring is genetically different from any others.
Meiosis produces haploid daughter cells.
Four
Meiosis halves the chromosome number from to .
diploid / haploid
Genome
The entire set of the genetic material of an organism.
Gene
A section of DNA that codes for a particular sequence of amino acids, which form proteins.
DNA
Deoxyribonucleic acid – the genetic material found in the nucleus of a cell. It is a polymer made of two strands coiled into a double helix.
What was the Human Genome Project?
A 13-year project, completed in 2003, in which scientists sequenced the genes that make up the whole human genome.
What is a single nucleotide made of?
A sugar, a phosphate group, and one of four different bases attached to the sugar.
Which bases pair together in DNA?
Adenine pairs with Thymine (A–T)
Cytosine pairs with Guanine (C–G)
What holds the two strands of the DNA double helix together?
Weak hydrogen bonds between the complementary base pairs.
Name the four bases found in DNA.
Adenine (A), Cytosine (C), Thymine (T) and Guanine (G).
When extracting DNA from fruit, why are detergent and salt used?
The detergent breaks down the cell membranes and nuclear membranes, releasing the DNA.
The salt causes the DNA to stick together.
When extracting DNA from fruit, why is ice-cold ethanol added and what is seen?
DNA is not soluble in cold alcohol, so it precipitates (comes out of solution), appearing as a stringy white precipitate.
DNA is a polymer made of two strands coiled together to form a .
double helix
Complementary base pairs are held together by weak bonds.
hydrogen
Sign up to unlock flashcards
or