Patterns of Inheritance Flashcards
Causes of phenotype variation
The appearance of a living organism (phenotype) is influenced both by its genotype (genetic makeup) and environment
What is a mutation
Change in the genetic material
-Structure of DNA
-Change to structure/ gross number of chromosomes
What is a mutagen
Certain physical/ chemical agents that cause mutations
Physical mutagen agents e.g.
-X-rays
-Gamma rays
-UV light
Chemical mutagen agents e.g.
-Benzopyrene (in tobacco smoke)
-Mustard gas
- Nitrous acid
Biological mutagen agents e.g.
- Some viruses
-Transposons - jumping genes, remnants of viral nucleic acid that have become incorporated into our genome
-Food contaminants i.e. mycotoxins from fungi
Mutations that occur during gamete formation
Can be advantageous/ neutral/ harmful
-Persistent: Can be transmitted through many generations without change
-Random: Not directed by a need on the part of the organism in which they occur
When do chromosome mutations occur
Meiosis
Types of chromosome mutations
-Deletion
-Inversion
-Translocation
-Duplication
-Non-disjunction
Deletion (Chromosome mutation)
Part of a chromosome (containing genes and regulatory sequences) is lost
Inversion (Chromosome mutation)
Section of the chromosome may break off and turn 180 degrees and then join again
=Although all genes are still present, some may now be too far away from their regulatory nucleotide sequence to be expressed
Translocation (Chromosome mutation)
A piece of one chromosome breaks off and attaches to another chromosome
-May also interfere with the regulation of genes on the translocated chromosome
Duplication (Chromosome mutation)
A piece of the chromosome may be duplicated
-Overexpression of genes can be harmful, as too many of certain proteins/ gene regulating nucleic acids, may disrupt metabolism
Non-disjunction (Chromosome mutation)
One pair of chromosomes/chromatids fails to separate, leaving one gamete with an extra chromosome
=When fertilized by a normal haploid gamete, the resulting zygote has one extra chromosome
What diseases are caused by Non-disjunction
Down syndrome / trisomy 21
Two types of Non-disjunction
-Aneuploidy
-Polyploidy
Aneuploidy
The chromosome number is not an exact number of the haploid number for that organism
-Sometimes chromosomes/chromatids fails to separate during meiosis
All in pairs but one set has an extra chromosome i.e. chromosome 21 has an extra chromosome which results in the disease trisomy
Polyploidy
Polyploidy- more than two copies of chromosomes
Diploid - meiosis error = instead of producing haploid egg and sperm it produces diploid egg and sperm
2n+ 2n = tetraploid plant
When diploid+ tetraploid fertilise
n+ 2n = 3n it will produce a triploid plant (non-viable and infertile)
Species
Interbreed; produce fertile offspring
How does sexual reproduction increase genetic variation
- Allele shuffling: P1
-Independent assortment: M1+A1/M2/A2
-Ransom fusing of gametes
Environmental factors that cause variation
-Speaking with a particular regional dialect
-A scar
Genetic factors that cause variation
-Blood group
-Tongue rolling
Genetic and Environmental factors that cause variation
-Skin colour
-Intelligence
-Sporting mass
-Body mass
-Height
How is variation caused by the environment interacting with genes
If plants are kept in dim light after germination/ soil contains insufficient nutrients then leaves do not develop enough chlorophyll
-Plant described as chlorotic + cannot photosynthesise
=Chlorotic plants have the genotype to make chlorophyll but environmental factors prevent them from expressing this gene