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)
Critical Values Table
D.F. = n - 1
p values: 5% significance (p=0.05)
IF chi-squared value is LESS than the critical value at 5% significance, the Null Hypothysis CAN NOT be Rejected (accept null hyp.) = No Significant Difference
IF chi-squared value is MORE than the critical value at 5% significance, the Null Hypothysis is REJECTED = some other factor is causing a Significant Difference
What is Epistasis?
the Interaction of Genes at Different Loci.
Gene Regulatiopn is a form of Epistasis, with regulatory genes controlling the activity of structural genes.
Many genes interact Epistatically.
Define ‘Epistatic Gene’
a Gene that Affects the Expression of another gene
Define ‘Hypostatic Gene’
a Gene Affected By Another Gene
Recessive Epistasis
When a Recessive allele of one gene Masks the Effects of either allele of the Next gene
- if the presence of 2 Recessive alleles at a gene locus led to the lack of an enzyme
Dominant Epistasis
When a Dominant Allele of one gene masks the expression of all alleles of another gene
Only takes One dominant allele for the organism to have the trait
Natural Plant Cloning
Bulbs
Runners
Rhizomes
Stem Tubers
Bulbs
Leaf base swells with food stores
Buds form internally, which develop into new shoots and new plants in the next growing season
e.g. Daffodils
Runners
Lateral stem grows away from the plant
Roots develop where runner touches ground & new plant develops
Runner eventually withers, leaving a new plant
e.g. Spider plants or strawberries
Rhizomes
a specialised horizontal stem running underground, often swollen with food stores.
Buds develop and form new vertical shoots, which become independent plants
e.g. Marram Grass
Stem Tubers
The Tip of an underground Stem becomes Swollen with Food stores, forming a tuber or storage organ.
Buds on the Storage organ Develop to produce New Shoots, e.g. Eyes on a potato.
Natural Clones in Horticulture
split bulbs
remove plants from runners
cutring up rhizomes
Cuttings
= short sections of stems are taken and planted into pots or the ground.
Rooting Hormone may be applied at base of cutting to encourage growth of new roots
+fast
+guarenteed quality of plant
-lack of genetic variation
Causes of Chlorosis
Lack of light
Mineral deficiency
Viral infection
