Inheritance & Biotech Flashcards
What is Chlorosis?
leaves of plant look pale/yellow due to cells not producing the normal amount of chlorophyll - this reduces the plants ability to photosynthesise.
Animal Body Mass
determined by Combination of both Genetic and Environmental factors
Environmrntal: amount & quality of food eaten, Quantity of Exercise, Disease.
Genetic: Obese Mouse has a mutation on chromosome 3 which causes the pattern of fat deposition to change and leaves the individual fatter
What is Genetic Variation?
Diversity in gene frequencies.
Rises as a result of mutation and is Essential to Natural Selection & Evolution
What determines the Individual mixture of alleles an organism inherits/Genetic Variation?
Meiosis - Crossing-over & Independent assortment
Random Fertilisation/Fusion of gametes
Define Homozygous
2 identical alleles for a characteristic
Define Heterozygous
2 different alleles for a characteristic
What is Continuous Variation?
A characteristic can take any value between 2 extrems.
Polygenetic
E.G. Height, Weight, Leaf surfaces area
What is Discontinuous Variation?
A characteristic can only appear in specific (discrete) values/groups.
One or Two genes
E.G. Blood group, Albinism, round/wrinkled pea shape
True breeds / Pure Breeds
Organisms that contain homozygous alleles for a particular gene
Two Breeding individuals are crossed:
all offspring are Heterozygous
F1 Generation
Two Heterozygous individuals are crossed:
3:1 (Dominant:Recessive)
F2 Generation
Codominance
Occurs when two alleles occur for a gene an both are equally dominant, so both are expressed in the phenotype of the organism.
E.G. Snapdragon flowers
heteroxygous = Pink flowers
alleles represented in superscript on letter representing gene.
Multiple Alleles
Some genes have More than 2 Versions. E.G. Blood Group; antigen A, B, & O A and B are codominant, O is recessive A = AA or AO B = BB or BO AB = AB O = OO
Determining Sex
Sperm that fertilises the egg (X) will have an X or Y chromosome.
Sex Linked Genes
Sex Linkage
Characteristics determined by genes carried on Sex Chromosomes.
Y is smaller than X so tere are many genes on the X that men only have 1 of, leading to characteristics caused by a recessive allele (on the missing section of the X) occurs more frequently in males, since females are likely to also have a dominant allele present in their cells.
What is Haemophillia?
Sex-linked genetic disorder
caused by Recessive allele = most sufferes are male
Blood clots slowly due to absence of a protein blood-clotting factor.
Heterozygous females = Carriers (do not suffer)
What is Dihybrid inheritence?
Inheritence of 2 genes
Shown by a dihybrid cross
What is a Dihybrid Cross?
Four alleles (2 for each characteristic) are shown at each stage, Expected ratio for 4 different phenotypes F2 = 9:3:3:1
Why does the Expected and Actual ratios differ?
Fertilisation of Gametes is Random
Small sample may skew ratio
Linked Genes - genes studied are on the same chromosome.
What is Autosomal Linkage?
linked genes on a non-sex chromosome
Linked genes are inherited as one unit together - there is no independent assortment unkess the alleles are separtaed by chiasma between (unlikely)
What are Recombinant Offspring?
offspring with a Different Combination of Alleles than either Parent
- unlikely to be produced when genes are close/linked
Chi-Squared Test
statistical test which measures the size of the difference between the observed and expected results.
It helps determine if the differences are significant or not; prove or disprove null hypothesis (Significant difference?)
Large chi-squared value
= statistically significant difference between the observed and expectred results
Probability that difference are due to Chance is Low
- there must be another reason
calculation for Degrees of Freedom
n-1
n = number of categories or possible outcomes (e.g. phenotypes)
