Inheritance, variation and evolution Flashcards
How many chromosomes does a human cell content
23 pairs of chromosomes in the nucleus
How many chromosomes does a human sperm and egg cell both contain
23 single chromosomes
How can cells divide
By mitosis (In mitosis one so is copied into 2 identical daughter cells)
Name 2 gametes
Sperm cell and Egg cell
How are gametes made
By cell division (Meiosis)
Unlike mitosis what does meiosis produce
Non-identical cells (every sperm cell and every egg cell are different)
meiosis takes place in flowering plants (Pollen and egg cells)
What do animals and flowering plants carry out
Sexual reproduction
What does sexual reproduction involves
Fusion of male and female gametes
Mixing of genetic information (DNA) the offspring receives genetic information from both the male and female parents
What does fusion mean
Joining together (Fertilization)
What’s the difference between sexual and asexual reproduction
Asexual reproduction involves one parent but sexual involves two people
What does asexual reproduction not involve
Gametes this means meiosis will not take place
Asexual reproduction are all genetically identical What do scientists called this
Clones (Mitosis=2 identical cells)
Where does meiosis take place
In reproductive organs
Cells in the reproductive organs divide by meiosis to form what
Gametes
How do gametes join
By fertilization to restore the number of chromosomes
Meiosis takes place in the reproductive organs what is this for men and women
In men it’s the testes
In females it’s the ovaries
Explain the stages of meiosis
In the first stage of meiosis all of the chromosomes are copied (in pairs) then the cell divides into 2 and both of these cells divide one more time forming the gametes (In the gametes the chromosomes are single) 
At the start of meiosis chromosomes are in pairs but at the end of meiosis the chromosomes are gametes that are single what does this mean
Meiosis has halved the number of chromosomes
From one original so what does meiosis produce
4 gametes and each are genetically different from each other (each gamete has different alleles)
In sexual reproduction gametes from the male and female join together what is this called
Fertilization
What happens after fertilization
The new cell divide by mitosis (producing a clump of identical cells=Embryo) and the number of cells increase as the embryo as it develops cells differentiate forming different cell types (ex. Mussels)
What does DNA consist of
2 strands and each strand is a polymer (each strand is made by joining together lots of smaller molecules)
The DNA is a polymer made up of two strands what does it form
A double helix
The DNA is contained instructions what is this called
Chromosomes
What is a gene
A gene is a small section of DNA on a chromosome
The genetic material in the nucleus of a cell is composed of a chemical what is this called
DNA
How are proteins made
By joining together amino acids
What does each gene encode for
A specific sequence of amino acids to make a specific protein
What is the genome
The genome is the entire genetic material of an organism (it makes up humans)
How can scientists use the information about the whole human genome in the future
To make medicine
Understanding the human genes will help us to search for genes that are linked to diseases give some examples
The risk of developing cancer or Alzheimer’s disease
What does understanding the human genome help us with
Understanding and treat inherited disorders example. cystic fibrosis
Research about the risk of developing cancer or Alzheimer’s disease
We can use it to trace human migration patterns from the past (Helping people discover their ancestry)
What are alleles
Alleles are versions of a gene
How many pairs of chromosomes control the characteristics of a human
22 pairs control characteristics but one of the pairs carries the gene that determines the sex