B11 - Inheritance Flashcards
Inheritance
The transmission of genetic information from generation to generation
Chromosomes
Located in the nucleus, they are thread-like structures of DNA, carrying genetic information in the form of genes
Gene
A short length of DNA found on a chromosome that codes for a specific protein
* control our characteristics as they code for proteins and play roles in what cells do
Alleles
Different versions of a particular gene
* like blood types
* they give all organisms their characteristics
Sex chromosomes
Males: XY
Females XX
* therefore, the father is responsible for determining the sex of the child
Karyotype
An individual’s complete set of chromosomes
Haploid nucleus
A nucleus containing a single set of unpaired chromosomes
* e.g. in gametes with 23 chromosomes
Diploid nucleus
A nucleus containing two sets of chromosomes
* e.g. in body cells with a pair of 23 chromosomes (46 overall)
Punnet square
A table in which all of the possible outcomes for a genetic cross between two individuals with known genotypes are given
* one pair of alleles on x and an other on the y-axis
* their combinations give us the ratios of the possible outcomes
Mitosis
Nuclear division giving rise to genetically identical cells
Process of mitosis
- Just before mitosis, each chromosome in the nucleus copies itself exactly (forms x - shaped chromosomes)
- Chromosomes line up along the centre of the cell where cell fibers pull them apart
- The cell divides into two; each new cell has a copy of each of the chromosomes leaving all resulting cells as a diploid nucleus
Where does mitosis occur? (3)
- Growth: produces new cells
- Repair: replace demaged or dead cells
- Asexual reproduction: produces offspring that are genetically identical to parent
Stem cell
Unspecialised cells used to divide by mitosis and produce new daughter cells that can become specialised
Meiosis
Nuclear division that gives rise to cells that are genetically different
* used to produce gametes
* is a reduction division: chromosome number is halved from diploid to haploid
Process of meiosis
- Each chromosome makes identical copies of itself (forming X-shaped chromosomes)
- First division: chromosomes pair up along the centre of the cell, recombination occurs and then cell fibres will pull the pairs apart, each new cell will have one of each recombinant chromosome pair
- Second division: chromosomes will line up along the centre of the cell, cell fibres will pull them apart (as with mitosis)
- A total of four haploid daughter cells will be produced
Differences between mitosis and meisos (name 3)
Mitosis:
* two cells produced (daughter cells)
* daighter cells are diploid
* daughter cells are genetically identical to each other and to parent cell
* one cell division occurs
Meisois:
* four cells produced (daughter cells)
* daughter cells are haploid
* daughter cells are genetically different from each other and parent cell
* two cell divisions occur
Phenotype
The observable characteristics of an organism (seen just by looking - like eye colour, or found – like blood type) is called the phenotype