Lecture 29. Mendelian Inheritance Flashcards
What is a gene?
A unit of inheritance, a section of DNA sequence encoding a single protein
What is a genome ?
The entire set of genes in an organism
What is an allele ?
Two genes that occupy the same position on homologous chromosomes and that cover the same trait
What is the locus ?
A fixed location on a strand of DNA where a gene or one of its alleles is located
What does the term homozygous mean ?
Having identical genes (one from each parent) for a particular characteristic
What does the term heterozygous mean ?
Having two different genes for a particular characteristic
What does the term dominant mean ?
The allele of a gene that masks or suppresses the expression of an alternate allele; the trait appears in the heterozygous condition
What does the term recessive mean ?
An allele that is masked by a dominant allele, it does not appear in the heterozygous condition only in the homozygous
What is the genotype ?
The genetic makeup of an organism
What is the phenotype ?
The physical appearance of an organism (genotype + environment)
What is a monohybrid cross ?
A genetic cross involving a single pair of genes
What does P stand for ?
Parental generation
What does F1 stand for ?
First generation offspring from a genetic cross
What does F2 stand for ?
Second generation of a genetic cross
What did Mendel work with ?
Pure lines of peas
Prior to Mendel what was heredity and offspring regarded as ?
Heredity was regarded as a blending process and the offspring were essentially a dilution of the different parental characteristics
What was Mendel the first biologist to do ?
To use maths to explain results quantitatively
What did Mendel predict ?
- The concept of genes
- That genes occur in plants
- That one gene of each pair is present in the gametes
What were the 7 traits Mendel examined ?
- Round or wrinkled
- Yellow or green
- Purple or white petals
- Inflated or pinched ripe pods
- Green or yellow pods
- Axial or terminal flowers
- Long or short stems
What are the two types of alzheimers ?
- Genetic
2. Sporadic
What can alzheimer’s caused by ?
Build up of plaque (amyloid)
What is Mendel’s principle of dominance ?
Independent segregation of 2 alleles
What is Mendel’s principle of segregation ?
Independent assortment of 2 characters
What is Mendel’s law of dominance ?
One factor in a pair of traits dominated the other in inheritance unless both factors in the pair are recessive
What gene is effected in age related muscular degeneration and what is its position ?
- Rhodopsin gene
2. 3q
How would you find the combined probability of two traits occurring, for example yellow and round ?
By multiplying the probability of yellow occurring by the probability of round occurring
What is linkage ?
Tendency of genes from the same chromosome to remain together when they enter the gamete
What is recombination ?
The appearance of new combinations of alleles
What is termed a Mendelian disease ?
When mutations in a single gene cause a disease
What are some examples of Mendelian disorders ?
- Cystic Fibrosis
- Leber’s congenital amaurosis
- Huntington’s disease
- Haemophilia
What type of inheritance does Huntington’s disease have ?
Autosomal dominant inheritance
When may inheritance of characters by a single gene deviate from simple Mendelian patterns ?
- When alleles are not completely dominant or recessive (dosage sensitivity)
- When a gene has more than two alleles
- When a gene produces multiple phenotypes
What were Alfred Sturtevant ideas ?
- Proposed that percentage recombinants could be used to measure distance between genes
- Constructed the first genetic map
In humans, how many chromosomes do somatic cells have ?
46
In humans, how many pairs of chromosomes do somatic cells have ?
23
What does the term diploid mean ?
Two versions of each gene
What does the formation of germ cells require ?
Require a reduction division or meiosis
What is the process of meiosis ?
Homologous chromosomes pair up at metaphase 1, and each segregates into a different germ cell
