Inheritence Flashcards
What is DNA
A massively long structure which super coils itself around proteins in the body in order to form chromosomes. These are ‘X-like’ structures which tidy up the nucleus.
Why do the DNA latch onto proteins in the body?
Because they are readily available
What is the purpose of super coiling.
It tidied up he nucleus due to tight coiling and allows everything to fit
Where are genes found?
On the chromosomes
Genes are bands on chromosomes
Female gene formation
XX
Male gene formation
XY
What determines whether the child will be a boy or a girl?
The sperm
Describe how genes, chromosomes and DNA are all linked
The DNA form chromosomes, which contain small structures called genes on them.
Where are chromosomes found
In the nucleus
How many chromosomes are there in most human cells
46
How many pairs of non sex chromosomes are there and what are their names
Autosomes
22 pairs
How many pairs of sex chromosomes are there?
One, labelled X and Y
A=
T
C=
G
On the structure of DNA, what does the s stand for
Sugar
On the structure of DNA, what does the p stand for
Phosphate
On the structure of DNA, what is G bonded with C labelled as
Nitrogenous bases
What is a base, bonded with sugar and phosphate labelled as?
A nucleotide
What is mitosis
A form of cell division that produces two identical diploid daughter cells from a diploid body cell, used for growth and repair in the body and in asexual reproduction. It occurs in all body cells apart from gametes.
What are the stages of mitosis
Interphase Prophase Metaphase Anaphase Telophase
(PMAT)
Mitosis chromosomes
Starts off with 46
Goes through DNA replication and has 92
Then separates into daughter cells which each have 46
Interphase
Before mitosis occurs
90 % of the cycle
DNA replication occurs in it (46-92)
This is because you have to duplicate the genetic material in the cell before splitting, or else they would not have the correct number of chromosomes.
Prophase
Nuclear envelope disintegrates
DNA supercoil to form chromosomes
The chromosomes take an X structure
Metaphase
Chromosomes attach to the equator of the cell ‘line up’
Anaphase
Spindle fibers drag chromosomes to the piles of the cell.
Chromosomes are pulled to the ends of the cell
Telophase
The nucleur envelope reforms around the chromosomes, which then unwind.
The cell divides (cytokinesis)
Two diploid daughter cells form, each containing 46 chromosomes
What is the purpose of mitosis?
- growth
- asexual reproduction
- repair of the tissue
- cloning
What cells would meiosis make?
Gametes
What happens in meiosis?
You have to go through PMAT twice in meiosis because otherwise when the sperm and the egg got together in reproduction, there would be too many chromosomes and they wouldn’t function.
Meoisis chromosomes
46 92 - DNA replication PMAT 46 46 PMAT 23 23 23 23 haploid daughter cells
Haploid
Half the genetic number of chromosomes
Diploid
Normal amount of chromosomes
Why is it important that humans endure meiosis?
Because variation is needed so meoisis creates non- identical daughter cells and sexual reproduction also creates variety
What is an allele?
Different versions of the same gene
Different characteristics
E.g. hair colour gene.
Phenotype
The visible physical appearance of an organism based on the expression of genes
Heterozygous
The alleles in the organisms are different
Homozygous
Both alleles in the organism are identical
Recessive
And allele which is only expressed when it is with another identical allele.
Dominat
And allele that is always expressed even when it is paired with another allele
Genotype
The genetic composition of an organism
A gene is
A section of molecule of DNA and a gene codes for a protein
DNA molecule
Two strands coiled to form a double helix, linked by a 4 nitrogenous bases AT CG
What are alleles
Alternative forms of genes which give rise to differences in inherited characteristics
Why do cells need to divide
To replace worn out cells form growth and to replace dead cells
List 3 places in ur body where mitosis occurs
Skin, blood, bone marrow
When a genetic material of a cell changes it is called
Mutation
Describe the relationship between genes and the characteristics of an organism
Each gene codes for a specific protein, the proteins will determine the phenotype
Advantages of reproducing sexually
Varied species
2 parents to raise offspring
More chance of survival
Prevents monoculture
Why self-pollinate?
To stop cross pollination
To control the gene pool or prevent other genes getting in
Environmental factor that may increase the probability of a random gene mutation
UV, x ray, tar from cigarettes
