Inheritance,genes & Chromosomes Flashcards

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1
Q

What are the 2 theories emerged to explain breeding experiments ?

A

Blending inheritance -gametes contain hereditary determinants that Blending in the zygote.offspring phenotypes are intermediate

Particular inheritance-hereditary determinants are distinct and remain intact at fertilization

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2
Q

What is Mendel’s monohybrid experiment ?

A

When 2 strains of peas with contrasting traits are bred their characteristics are irreversibly blended in succeeding generations

Plant true breeding round seed and true breeding wrinkled seed
no blending- F1 -1 dom trait present
2 filial generation both dom & rec traits present in ratio of 3:1
Hypothesis is rejected -no irreversible blend of characteristics & rec trait can reappear in succeeding generation

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3
Q

Inheritance genes follows Mendelian law

A

Mendel proposed that hereditary determinants occur in pairs & segregated from one another during formation of gametes
Parental generation (P) = ♂ RR x ♀ rr
Gametes R R. r r
Each pea plant offspring would inherit one of its pair of heredity determinants from each parent

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4
Q

What is an allele ?

A

When gene has different forms causing different traits
Different version of the same gene

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5
Q

Define homozygous ?

A

Organism which has a gene for 2 alleles that are the same

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6
Q

Define heterozygous ?

A

Organism that has genes which have 2 different allele
One may be dominant over the other the presence of a recessive allele explains how a trait could reappear in the next generation

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7
Q

Define Phenotype ?

A

Is the physical appearance of an organism

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8
Q

Define Genotype ?

A

Is the genetic constitution of an organism

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9
Q

What did Mendel propose ?

A

That the phenotype is the result of the genotype
Only when you have 2 recessive alleles will you see the recessive phenotype

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10
Q

MENDELS FIRST LAW ?

A

The law of segregation:
The 2 copies of a gene separates during gamete formation ;each gamete receives only one copy

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11
Q

Mendels 2nd law ?

A

Independent assortment : copies of different genes assort independently

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12
Q

Define codominance

A

2 alleles produce phenotypes that are both present in heterozygote

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13
Q

How blood group system ?

A

The ABO blood group system results from an enzyme that adds specific groups to oligosaccharides in red blood surface

IA &IB alleles prod diff versions of the enzyme
IO allele prod neither

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14
Q

Define Epistasis ?

A

Phenotypic expression of 1 gene is influenced by another gene

Coat colour in Labrador retrievers is determined by the colour gene B:
But for alleles B (black) and b (brown) to be expressed, allele E of a separate gene (pigment deposition) must also be expressed.
An ee dog is yellow regardless of which B alleles are present. Gene E is said to be epistatic to gene B.

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15
Q

What affects phenotype ?

A

Environment
Eg) point restriction in Siamese cats and rabbits an enzyme that produces dark fur is inactive at higher temp s most fur is white even though allele to prod enzyme is present
Expressivity: degree to which genotype is expressed in an individual

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16
Q

Define quantitative variation ?

A

Usually due to multiple genes and environment
Phenotypes vary continuously over a rage-quantitative/continous ,variation
Mendel=qualitative

17
Q

Genetic transformation of non-virulent pneumococci ?
Experiment

A

Hypothesis- material in dead bacterial cells can genetically transform living bacterial cells

Conclusion- a chemical substance form one cell is capable of genetically transforming another cell

Experimented in mice

18
Q

What is DNA made of ?

A

Base + deoxyribose = nucleoside & base + phosphate group =
Phosphate+nucelotide+ base

19
Q

What are the bases called and what are they ?

A

Pyrimidines-
Cytosine (C) & Thymine (T)
Purines- (2 rings)
Adenine (A) & Guanine (G)

20
Q

What is Chargraffs rule ?

A

amount of A= amount of T
amount of C = amount of G
Purines = Pyramidines

21
Q

How was the structure of DNA revealed ?

A

X-ray crystallography revealed

An X-ray source is projected onto a lead screen where its crystallised and then the beam of x-rays goes through the DNA sample where it then refracts through a photographic plate where an image is made
Franklin and Wilkins

22
Q

Base pairing ?

A

DNA consists of 2 antiparralel strands