Genetics And Cell Division Flashcards
What shape is DNA
Double helix
What small molecules are DNA made of
Nucleotides
How many bases does DNA have
4
What are the 4 bases for DNA
A - adenine
c- cytosine
G- guanine
T- thymine
Each base on a nucleotide forms what bonds to the complimentary base pairing on the other Strand?
Hydrogen bonds
What are the complimentary base pairing
Adenine - thymine
Cytosine - guanine
What does DNA control the production of
Proteins (protein synthesis) in cells
What is a gene
A section of DNA that codes for a particular
Protein
What are proteins made up of
Chains of amino acids
Each protein has its own particular number and order of amino acids
What decides the order of amino acids in a protein
The order of the bases in a gene
why can’t DNA molecules move out of the nucleus
Becasue they’re are very large
Where does protein synthesis happen
In the cytoplasm at organelles called ribosomes
As DNA can’t leave the nucleus amd protein synthesis happen in the cytoplasm on ribosomes what happens
A copy of the gene that codes for it is made in the nucleaus. This copy is smaller than the DNA so it can move into the cytoplasm where it can be used to make the protein
In protein synthesis the copy of the gene is made from a molecule called ?
Messenger RNA (mRNA)
DNA is used as a —— to make - - - molecule
Template
mRNA
what is RNA made up of
Nucleotides
Which each have a base
The bases on the RNA nucleotides line up next to their complementary bases on what?
The DNA template
What base is not on RNA
Thymine (T)
As there is no thymine in RNA what binds to any adenine in DNA instead
Uracil (U)
Once the bases om RNA nucleotides have paired up with the bases on the dna strand the, the rna nucleotides join together to make an ?
mRNA molecule
How many bases code for one amino acid
3
3 bases in a row is known as what
A triplet
Differnt amino acids are coded for by differnt triplets eg
TAT=
AGT=
Tyrosine
Serine
What are mutations
Changes to the base sequence of DNA
How does mutation work (substitution)
One base can be swapped for another
This can cause a triplet to change
So mutation can change the amino acids in the protein that the gene codes for
A change in amino acids can cause a differnt protein to be produced
Sometimes the change in protein can be harmful
How often do mutations happen
Spontaneously
How can frequency of mutations be increased
Mutagenic agents
Examples of mutagenic agents
UV radiation in sunlight
How can mutations cause cancer
As cell division is controlled by proteins.
If mutations occur in the gene for these proteins, they can alter the proteins so they no longer work.
This can lead to the uncontrolled cell divison, and the development of a tumour
How can mutations cause genetic disorders
Mutations that result in altered genes and proteins can be inherited
Where is DNA. Found
In chromosomes in nucleus of eukaryotic cells
How many genes in each human chromosomes
Between a couple hundred and a few thousands
How many pairs of chromosomes do humans have
23pairs (46 in total)
One from each pair comes from your mother and one from your farther
T or f
All chromosomes in a pair are the same size and carry the same genes, they are known as homologous pairs
F
There is an exception of X and Y sex chromosomes
Do chromosomes in a homologous pair usually have differnt alleles
Yes
What is an X shaped chromosomes
One chromosomes attached to an identical cop of itself.
Not homologous pairs - only shaped just after the DNA has been replicated
Each side of an x-shaped chromosome is known as what ?
What is the area in the middle known as
Chromatid
Centromere
When is mitosis needed
For growth and repair
If you have damaged tissue, the cells around the damaged area divide by mitosis to replace damaged cells
Does asexual reproduction involve mitosis or meiosis
Mitosis
What is asexual reproduction
A single organism produces offspring by dividing into two organisms or by splitting of a piece of itself
All the offspring are genetically identical
The cells divide by mitosis
How many stages is mitosis split into
4
What are the 4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
What is the period before mitosis starts called
Interphase
Interphase
Before the cell starts to divide every DNA molecule (each chromosome) Must replicate to let each new cell has a full copy of DNA. The new molecule remains attached to the original one at the centromere
Prophase
Mitosis can now begin, each DNA molecule becomes supercoiled and compact
Each Kromozone can now be seen with a light microscope and appears as two chromatids lying side by side, joined by the centromere
Metaphase
The nuclear membrane breaks down and chromosomes lineup along the equator of the cell
Anaphase
The centromere split in the chromatids separate, and are dragged to opposite ends of the cell
Telophase
The nuclear membrane forms around each set of chromatids and the cytoplasm divides
Does sexual reproduction involve mitosis or meiosis
Meiosis
What is sexual reproduction
The offspring are genetically differnt from their parents and from each other. This produces variation in a population.
Each parent produces sex cells (gametes) containing just one set of genetic material- involves meiosis
During fertilisation the nuclei of the gametes join together to form a zygote
Zygote grows by simple cell division to form an embryo
Gametes only have one set of genetic material so are described as what?
Haploid
Zygote has two complete sets of genetic material so is described as?
Diploid
Where does meiosis take place
Testes
Ovaries
Examples of gametes
Sperm
Eggs
Explain meiosis
The DNA replicates, so each other 46 chromosomes becomes to Chromatids joined by a centromere
- Chromosomes sort themselves into 23 Homologous pairs then the pairs separate. One of each pair goes to one side of the cell, and one goes together.
The cytoplasm now divides each of the new cells contain 23 chromosomes.
In both of these new cells, the chromatids separate and the cytoplasm divides to form two cells
At the end of meiosis, four haploid cells have been produced from every original diploid cell
