Principles Of Inheritence And Variation Flashcards
What is inheritence
Process by which characters are passed on from parent to progeny
What is variation
The degree by which progeny siffer from their parents
From how early humans knew that causes of variation was hidden in sexual reproduction
8000-1000bc
Name an indian breed of animal formed by exploiting artificial selection and domestication
Sahiwal cows in Punjab
Timeline when Gregor Mendel did experiments on garden pea
Seven years(1856-1863)
When was the first time when statistical analysis and maths logic was applied in biology
During Mendel’s investigations
What is a true breeding line
One that has undergone continuous self pollination,shows stable trait inheritence and expression for several generations.
How many true breeding pea varieties Mendel used
14 in contrasting characters
Which were the seven characters used by Mendel
Seed shape,seed colour,pod shape,pod colour,flower colour, stem height,flower position
Which trait is dominant and recessive in flower position character.
Axial-dominant
Terminal-recessive
Which flower colour is dominant and recessive
Purple-dominant
White-recessive
What is called units of inheritence/unit of heredity
Genes
What are alleles
Genes which code for a pair of contrasting traits.
What is a monohybrid
A plant having heterozygous genes for one character only.all other character’s genes are homozygous.
What is a monohybrid cross
A cross between plants having contrasting genes for one character.
What is test cross
Cross between F2 plant and dwarf plant
Law of dominance and law of segregation were based on which type of cros
Monohybrid cross
What is the ne given to law of dominance and law of segregation
Principles or laws of inheritence
What are the postulates of law of dominance
Characters are controlled by discrete units called factors/genes
Factors/genes occur in pairs
In a dissmiliar pair of factors/genes one member of the pair dominates the other
What does law of dominance explain
Expression of only one of the parental character in a monohybrid cross in f1 and expression of both in f2
Also explains 3:1 of f2
What is law of segregation
The factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors.
What does law of segregation explains
Non blending of characters in progency.that both characters are recovered later.
Give example of incomplete dominance
Inheritence of Flower colour in the dog flower/snap dragon/antirrhinum
Scientific name of dog flower
Antirrhinum
What is incomplete dominance
It is a heterozygous condition in which one of the allele in a pair of genes do not produce any enzyme or produce non functional enzyme
What happens in co dominance
In heterozygous condition both the alleles of pair of genes produce their own products
What is it called when progeny resemble both the parents?
Co dominance
Give an example of co dominance
ABO blood grouping group
Abo blood groups are controlled by which gene?
I gene
How I gene expresses itself.
The plasma membrane of the rbc has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene.
I^a produce A type of sugars,I^b profuce B type of sugar and i produce no sugar.
How many genotypes of human blood type is possible
Six
How many phenotypes of abo blood group is possible
Four
What is multiple alleles?give example
When there are more than two types of alleles governing the same character.
Abo blood grouping of humans
As organisms are mostly diploid(have two alleles for a character).how can multiple alleles be found?
By population studies
From the angle of starch grain size,what type of dominance pea seeds show and from the angle of seed shape what type of dominance pea seeds show in heterozygous condition?
From the angle of seed shape,B gene seems to be dominant in Bb condition because round seeds are produced
But from the angle of starch grain size incomplete dominance is seen as the size is intermidiate.
Give example of how occasionally a single gene product may produce more than one effect phenotypically
Starch synthesis and seed shape in pea seeds
What is a dihybrid cross
A cross between organisms(pea plants) that differed in two characters(all other characters same)
How can 9:3:31 be found methamatically
By series combination multiplication of two monohybrid cross
3round:1wrinkled)(3yellow:1green
On the basis of which cross Mendel proposed another genralisation law of independent assortment?
Dihybrid cross
What is law of independent assortment?
In a dihybrid cross,segregation of one pair of chatacters is independent of other pair of charcters.
Means theres is 25%frequency of zygote having ry,RY,Ry or rY genes.
When did Mendel published his work
1865
When and which scientists rediscovered Mendel’s work independently?
In 1900s deVries,
Correns and
von Tschermak .
By which year chromosomal movement during meiosis had been worked out?
1902
Who noted that the behaviour of chromosomal movement was parallel to genes and used chromosomal movement to explain Mendel’s laws
Walter Sutton and Theodore Boveri
What did sutton and boveri argued?
They argued that pairing and separation of pair of chromosomes would lead to the segregation of a pair of factors they carried.
Who created chromosomal theory of inheritence?how?
Sutton,
By uniting the knowledge of chromosomal segregation with mendelisn principle.
Whose experiments on verification of chromosomal theory of inheritence led to the discovery of the basis for the variation that sexual reproduction produced?
Thomas Hunt Morgan.
On which animal Thomas Hunt Morgan worked?
Fruit flies(Drossophila melanogaster)
In drossophila which sex is bigger ?
Female-bigger
Male-smaller
What Morgan did?what did he observed?
He carried out several dihybrid crosses in drossophila to study sex linked genes.
He observed the ratio in f2 deviated significantly from 9:3:3:1.
It meant two genes do not segregate independently as expected when genes are independent.
When was frequency of parental combinations were much higher?
When two genes are located on a same chromosome in a dihybrid cross.
aka When genes are linked
What did Alfred Strutvent did?
He used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between them and mapped their position on the chromosome.
Which type of sex determination mechanism grasshopper follow
XO type
Which type of sex determination mechanism birds/fowl follow?
ZW
What is male heterogamety and female heterogamety
When two diff type of gametes are produced by parent it is called heterogamety .
If male -male heterogamety
If female produce two types of ganetes -female heteroganety
What did Henking saw and when?
In 1891,henking traced a nuclear structure all through spermatogenesis,50%sperms had it 50%didn’t.
He called it X body.
Which was later found that it was a chromosome.now called x chromosome.
Why X chromosome is called sex chromosome?
Due to its involvement in sex determination
What are the two major types of genetic disorders?
Mendelian disorders
Chromosomal disorders
What is the diff bet mendelian and chromosomal disorders.
Mendelian disorders-disorder due to alteration or mutation in single gene
Chromosomal-disorder due to abnormal arrangement(excess/or deficiency )of chromosomes
What kind of disease haemophilia is?
Sex linked recessive
A single protein of a cascade of proteins involved in the clotting of blood is affected
Queen Victoria was a carrier of which disease?
Haemophilia
What kind of disease sickle cell anemia is?
Autosomal recessive.
Sickle cell anemia is caused by?
Substitution of glutamic acid by valine at the sixth position of beta globin chain of haemoglobin molecule.
What causes substitution of amino acid in the globin protein?
Due to singke base substitution at the sixth codon of the beta globin gene from GAG to GUG.
What happens in sickle cell anaemia?
Haemoglobin polymerises under low oxygen tension causing the change in the shape of RBC.
What kind of disease phenylketonuria is?what happens in it.
Autosomal recessive.
Patient lacks and enzyme that converts the amino acid phenylaneline to tyrosine.
As a result phenylaneline is accumulated and converted into phenyl pyruvic acuds and other derivatives .
That causes mental retardation.
What does gene produce in normal people that is affected in phenyl ketonuria?
Enzyme phenyl aneline hydroxylase
Phynelketonuria is an example of which type of inheritence?
Pleiotropy
Besides multiple gene’s effect on single trait ,polygenic inheritence also takes into account?
Influence of envirnment
Effect of each allele in polygenic inheritence is_______?
Additive
What is aneuploidy and how it is caused?
Gain or loss of chromosomes is called aneuploidy.
Caused by failure of segregation of chromatids during cell division.
What is polypoidy?
Failure of cytokinesis after telophase results in a whole set of chromosomes in an organism called polypoidy.
Polyploidy is common in?
Plants
What is the cause of down’s syndrome?
Caused by additional copy of chromosome number 21(trisomy of 21).
Who first described down’s syndrome? And when?
Langdon Down in 1866.
Down syndrome individual has large head or small head?
Small round head
What causes klienfelter syndrome?what karyotype it has?
Presence of extra X chromosome.
Karyotype of 47,XXY
What causes turner syndrome?
Absence of one X chromosme.
45 chromosomes with XO.
Turner syndrome-(male/female)
Klienfelter sybdrome-(male/female)?
Turner-female
Klienfelter-male
Gene of sickle cell anemia patient has which codon?
GTG
CAC
Which creates GUG in mRNA.
1% crossover/recombination frequency means how much map unit distance?17%?
Unit distance.
17 map units
