Please enable JavaScript.
Coggle requires JavaScript to display documents.
B13 - Reproduction - Coggle Diagram
B13 - Reproduction
13.7
The chromosomes you inherit carry your genetic information in the form of genes. Many of these genes have different forms, or alleles. Each allele codes for a different protein. The combination of alleles you inherit will determine your characteristics.
Genetic terms
Homozygote: an individual with two identical alleles for a characteristic, e.g. BB or Bb
Heterozygote: an individual with different alleles for a characteristic, e.g. Bb
-
Phenotype: the physical appearance of an individual, e.g. brown hair and blue eyes
Genetic crosses
A genetic cross is when you consider the potential offspring that might result from two known parents.
Punnett squares
You can model genetic crosses using a genetic diagram like a Punnett square to pedict the outcome of different genetic crosses. This gives us:
-
-
How the gametes of the parents may combine to form the characteristic in their offspring, and the possible phenotypes
-
13.3
Asexual Reproduction
-
Disadvantages
If one organism can't survive, none can
-
Sexual Reproduction
Advantages
-
If the environment changes, the variation gives an advantage because some offspring will be able to survive
-
In plants, the gametes are the egg cells and pollen. In animals, the gametes are the egg cells (ova) and sperm.
13.9
Polydactyly
-
Polydactyly is commonly caused by a dominant allele inherited from one parent who also has the condition.
People often have their extra digit removed, but some people live quite happily with them
-
Cystic fibrosis
-
Disorder of the cell membranes that prevents the movement of certain substances from one side to the other. This causes the mucus made by cells in many areas of the body to become very thick and sticky. Organs (especially the lungs) can become clogged up by this mucus which stops them functioning properly. The pancreas can't make and secrete enzymes properly because the tubes through which the enzymes are released into the small intestine become blocked. The reproductive system is also affected, so many people with this disorder are infertile.
Treatment for cystic fibrosis includes physiotherapy and antibiotics to keep the lungs clear of mucus and infections. Enzymes are used to replace the ones the pancreas can't make and to thin the mucus. Treatments are improving, but there is still no cure for the disorder.
-
13.8
In humans, the female sex chromosomes are the same (XX), but the male sex chromosomes in humans are different (XY)
