Principles Of Inheritance And Variation Flashcards
Well known Indian breed of cow in Punjab -
Sahiwal
Gregor Mendel conducted hybridisation experiments on GARDEN PEA for _____years . From _to ____ .
7 yrs
1856-1863
During Mendel’s investigations into _____ it was for the first time that statistical analysis and mathematical logic were applied to biology .
Inheritance patterns
Mendels laws of inheritance
Mendels experiments had a _____ ,which gave greater credibility to the data he collected .
Large sampling size
Mendel conducted_______ experiments on ____breeding pea lines .
Artificial pollination /cross pollination experiments
True breeding
A true breeding line is one that , having undergone _________ , shows stable _____and _____for several generations .
Continuous self pollination
Stable trait inheritance
Expression
Mendel selected _____true breeding pea plant varieties as pairs , which were similar except for 1 character with contrasting traits .
14
Name the contrasting traits studied by Mendel in pea -
Stem height Flower colour Flower position Seed colour Seed shape Pod colour Pod shape
In F1 generation , ___trait as observed and in F2 , both the traits were expressed in the ratio_____ ( phenotypic ratio in monohybrid cross )
One of the parental trait only
3:1
Segregation meaning -
Separation ; isolation
Recessive parental trait is expressed without any _____ in the ____generation .
Blending
F2
When plants produce gametes by meiosis , the alleles of the parental pair ___ from each other and only 1 allele is transmitted to a gamete .
Segregate /separate
Segregation of alleles is a _____process .and there is ___chance of a gamete containing either allele .
Random
50%
Punnett square was developed by a ____ , named Reginald C Punnett .
British geneticist
When Mendel self -pollinated the F2 plants , he found that -
Dwarf F2 continued to generate dwarf plants in F3 and F4 .
Test cross is used to determine __composition .
Genotypic
______can be calculated using mathematical probability , by simply looking at the phenotype of a dominant trait , it is not possible to know ______ .
Genotypic ratios
Genotypic composition
Whether a tall plant from F1 or F2 has TT or Tt composition can be predicted using -
Test cross
In a typical test cross ,an organism showing a _____ and whose ____is to be determined , is crossed with the _____ instead of self-crossing
Dominant phenotype
Genotype
Recessive parent
Based on his observations on monohybrid cross , Mendel proposed 2 rules to consolidate his understanding of inheritance. These rules are called _____ . Name them .
Principles or Laws of Inheritance
1st law -law of inheritance
2nd law - law of segregation
Give the 3 postulates of LAW OF DOMINANCE -
1) chars are controlled by discreet units called FACTORS .
2) factors occur in pairs
3) in a dissimilar pair of factors one member if a pair dominates the other .
____law states that the ALLELES do not show any blending and that both the chars are recovered as such in F2 gen , though one of these is not seen at the F1 stage .
Law of segregation
Though the parents contain 2 alleles during gamete formation , the factors or alleles of a pair _____ from each other such that a gamete receives only one of the 2 factors .
Segregate
Sometimes the F1 had phenotype that did not resemble either of the 2 parents and was in btw the 2 . This phenomenon is called -
Incomplete dominance
The inheritance of flower colour in ______is a good example to understand incomplete dominance .
Dog flower /snapdragon/ Antirrhinum sp .
Ina cross btw true-breeding red-flower and true-breeding white flower , the ____ generation was ____.
The F1 gen
Pink ( all )
When the F1 gen ( all pink ) , were SELF POLLINATED , then F2 resulted in -
1 red : 2 pink : 1 white
If we talk about a gene that contains info for producing an enzyme , the modified allele (of the gene) could be responsible for production of -
Normal or less efficient enzyme
A non-functional enzyme
No enzyme at all
If the allele produces normal or less efficient enzyme , the modified allele is equivalent to the ____ i.e. , it will produce the ____ i.e., results in the transformation of substrate .
Unmodified allele
Same phenotype /trait
The ____allele which represents the original phenotype is the dominant allele and. The __is generally the recessive allele .
Unmodified /functioning
Modified
In the enzyme functioning , recessive trait is seen due to ____ or _____ .
Non-functional enzyme
Becoz no enzyme is produced
In case of ______, the______ resembles both the parents .
Codominance
F1 gen
Examples of codominance -
ABO blood grps
ABO blood grps are controlled by the gene ____.
I
The ____of the RBCs have _____that protrude from its surface and the _____is controlled by the gene .
plasma membrane
Sugar polymers
Kind of sugar
The gene I has __alleles . Name -
3
IA
IB
i
The kind of sugar produced by the 3 alleles is -
IA ad IB - produce a slightly diff form of sugar
i-does not produce any sugar
When ____and __are present together , they both express their own types of sugars .
IA
IB
Becoz of codominance , RBCs have ____types of sugars .
Both A and B
A total of ___genotypes of the human ABO blood types are possible .
6
ABO blood grouping also provide a good example of ______.
Multiple alleles (And codominance)
ABO show multiple allelism , becoz ?
Here , 3 alleles ( more than 2) are governing the same char .
Since in an individual only 2 alleles can be present , multiple alleles can be found occasionally only when ____are made .
Population studies
___is not an autonomous feature of a gene or the product that it has info for .
Dominance
Dominance depends as much on the ________and the production of _____.
Gene produce
Particular phenotype from this product
Occasionally , a single gene product may produce more than one effect . For example -
Starch synthesis in pea seeds -controlled by 1 gene
Starch is synthesised effectively by homozygotes (BB) , therefore ____starch grains are produced . After maturation , BB seeds are rounded and bb wrinkled . B is the dominant allele . But starch grain produce ____ size in Bb .
Large
Intermediate size
If starch grain SIZE is considered as the PHENOTYPE , then form this angle , the alleles show _____ .
Incomplete dominance ( in size )
When mendel self -hybridised the F1 plants , he found that ____ of F2 had yellow seeds and ____had green seeds. Therefore the yellow and green colour segregated in a _____ratio .
3/4th
1/4th
3:1
In a di hybrid cross , the PHENOTYPES round yellow ;wrinkled yellow ;round green ;wrinkled green appeared in the ratio -
9:3:3:1
Based on the observations on the di hybrid crosses , mendel proposed a second set of generalizations , that we call -
Law of independent assortment
State law of independent assortment -
When 2 pairs of traits are combined in a hybrid , segregation of one pair f characters is independent of the other pair of chars .
Mendel published his work on inheritance in ____ , but it remained unrecognised till ____ .
1865
1900
Give 3 reasons why mendels work remained unrecognised for several years -
1) communication was not easy
2) his concept of genes (or factors ) as stable and discreet units that controlled the expression of traits and of th pair of alleles that did not blend with each other was not accepted by his contemporaries .
3) mendels approach of using maths to explain biology was totally new .
In _____ , 3 scientists ____, ____ and ___ rediscovered mendels results on inheritance of chars .
1900
De vries
Correns
Von tschermak
The 3 scientists jointly /independently rediscovered mendels results .
Independently
By 1900 , due to advancements in microscopy scientists were able to observe ______ . This led to the discovery of structures in the nucleus that appeared to double and divide just before cell division . They were called _____ .why ?
Cell division
Chromosomes / coloured bodies
Becoz they were visualised by staining
B ___ , the chromosome movement during meiosis had been world out .
1902
__and ___noted that behaviour of chromosomes was parallel to the behaviour of genes .
Walter Sutton
Theodore boveri
Walter Sutton and Theodore boveri used __to explain __.
Chromosome movement
Mendels laws
__As well as _____occur in pairs .
Chromosomes
Genes
(Sutton and boveri )
The ____ of ___are located on homologous sites on homologous chromosomes .
2 alleles
A gene pair
During ____of ____ , the 2 chromosome pairs are aligned at the metaphase plate independently of each other .
Anaphase 1
Meiosis 1
___and ___ argued that the pairing and separation of a pair of chromosomes would lead to segregation of a pair of factors they carried .
Sutton
Boveri
Sutton united the knowledge of________ with______ principles and called it _______.
Chromosomal segregation
Mendelian principles
Chromosomal theory of inheritance
Who gave the chromosomal theory of inheritance ?
Sutton
Experimental verification of chromosomal theory of inheritance was done by -
Thomas hunt morgan
______led to discovering the basis for VARIATION that sexual reproduction produced .
Experimental verification of chromosomal theory of inheritance by Morgan and his colleagues
Morgan worked with the _____flies .
Fruit -drosophila melanogaster
Why were fruit flies found very suitable for Morgan’s study ?
1) could be grown on simple synthetic medium in the laboratory
2) they complete their life cycle in about 2 weeks
3) a single mating could produce a large number of progeny flies
4) clear differentiation of sexes
5) it has many types of hereditary variations that could be seen with a low power microscope
Morgan carried out several ___ crosses in drosophila to study genes that were ______.
Dihybrid
Sex-linked
The crosses carried out by Morgan were similar to the dihybrid crosses carried out by _____ in ____ .
Mendel
Peas
Morgan hybridized ____ females to ____males and ____their progeny .
Yellow bodied -white eyed females
Brown bodied -red-eyed males
Intercrossed
When Morgan performed the dihybrid cross , he observed that the 2 genes __________ and the F2 ratio deviated very significantly from the ______ .
Did not segregate independently of each other ( separated depending on each other )
9:3:3:1 ratio ( expected )
Morgan and his group knew that the genes were located on the _____.
X-chromosome
Morgan saw that when the 2 genes were situated on the same chromosome , the proportion of ____Were much higher than the _____ .
Parental gene combination
Non-parental type
Morgan coined the term ___ to describe the physical association of genes on chromosomes and the term ____ to describe the NON-PARENTAL gene combinations .
Linkage
Recombination
Morgan found that genes __ and __were tightly linked ( on drosophila ) and showed only ___% recombination .
White
Yellow
1.3%
Morgan found that ____and __wing were linked more tightly and showed ____% recombination .
White
Miniature
37.2%
Who was Morgan’s student ?
Alfred sturtevant
Alfred sturtevant used the _____betw gene pairs on the ____chromosome as a measure of the ______ and _____their position on the chromosome .
Frequency of recombination
Same
Distance btw genes
Mapped
Genetic maps were made by -
Alfred sturtevant
Genetic maps are extensively used as a starting point in the sequencing of whole genomes as was done in the case of the ______ .
HGS
Human genome sequencing project
Traits that are controlled by one or more GENES are called ____ . For ex -
Polygenic traits
Heights / skin colour
Besides the involvement of multiple genes , polygenic inheritance also takes into account the influence of ________ .
Environment
Human skin colour is a classical example of ______.
Polygenic inheritance
In a polygenic trait , the ___reflects he contribution of each allele i.e., he effect of each allele is ______.
Phenotype
Additive
As expected ,the genotype with 3 dominant alleles and 3 recessive alleles will have _____skin colour .
Intermediate
When a single GENE can exhibit multiple phenotypic expression , it is called -
Pleiotropic gene
The underlying mechanism of pleiotropy is the _________ .
Effect of a gene on metabolic pathways which contribute towards diff phenotypes
Example of pleiotropy -
Disease - phenylketonuria
Phenylketonuria is caused by _______ in the gene that codes for ______ . Therefore , it is also called _______.
Mutation
Enzyme phenyl alanine hydroxylase
SNGLE GENE MUTATION
Single gene mutation in phenylketonuria manifests itself through ______ characterised by _____, ____ and ______ .
Phenotypic expression
Mental retardation
Reduction in hair
Skin pigmentation
______in the year _____ could trace a specific nuclear structure all through spermatogenesis in a few insects .
Henking
1891
He king observed that __% of the sperm received this nuclear structure and ___% did not. Receive it . He king called this structure as the _____ .
50%
50%
X-body
Investigations by other scientists led to he conclusion that the ___ was in fact a chromosome and that is why it was given the name _____.
X-body of Henking
X-chromosome
It was observed that in a large number of insects , The mechanism of sex-determination is of the _______type .
XO type
XO type of sex-determination in insects is -
Eggs bear an additional X-chromosome besides the autosomes .
Some of the sperms bear the X-chromosome whereas some do not .
In insects , eggs fertilized by sperms having an X -chromo become ___ and those fertilised by sperms that do not have X-chromo become ___.
Females
Males
Due to the involvement of the X- chromo in the determination of sex , it was named __ while the rest of the chromo were named _____ .
Sex- chromo
Autosomes
_____is an example of XO type of sex deter where males have only one X chromo besides auto but females have a pair of X -chromo .
Grasshopper
In both humans and insects , __bar 2 types of gametes . Name
Males
With or without X-chromo
Some gametes with X and some with Y chromo
XO and XY type of sex-determination is designated to be -
Male heterogamety
In ____ a diff type of sex determination is observed .
Birds
In birds , the total number of chromo is same for __.
Both males and females
Female heterogamety is seen in -
Birds
The female bird has 1___and1___ chromo , whereas the male birds have ___ chromo besides autosomes .
Z
W
Pair of Z- chromo
____pairs of chromo are exactly same in both males and females .these are the __.
22
Autosomes
In males , during spermatogenesis . ___types of gametes are produced .
2
Sex-determination in honey bees is based on the -
No of sets of chromosomes an indivisual receives
In HONEY BEES ,an offspring formed from the union of sperm and an egg develops as a ___ and an unfertilised egg develops as a ____ by means of _____ .
Queen or worker - female
Male -drone
Parthenogenesis
Males are __And females are ___ . Ploidy in honeybees
Haploid
Diploid
Sex- determination in honey bees is called -
Haplodiploid sex deter
Special feature of haplodiploid sex -determination .
Males produce sperms by MITOSIS
Males do not have a father or son
But have a grandfather and grandson
Mutation is the phenomenon which results in the alteration of ____and consequently results in changes in the ____and the ____ .
DNA sequence
Genotype
Phenotype
Loss ( deletion ) or gain (insertion/duplication) of a segment of DNA results in _____ .
Alteration in chromosomes
Since __Are located on chromosomes , Alteration in chromosomes results in ___or ____.
Genes
Abnormalities
Aberrations
CHROMOSOMAL ABERRATIONS are commonly observed in ______.
Cancer cells -( cancer results due to mutation )
Mutation also arises due to change in _____. This is called ____
A single base pair of DNA
Point mutation
A classical example of point mutation -
Sickle cell anemia
Deletion and insertion of DNA causes ____.
Frame shift mutation
CHEMICAL and PHYSICAL factors that induce mutations are called -_____ . Ex -
Mutagens
UV rays
In human genetics , ____provides a strong tool which is utilised to trace the inheritance of a specific trait , abnormality or disease .
Pedigree analysis
Broadly , genetic disorders may be grouped into __Categories - ____and ___ .
2
Mendelian disorders
Chromosomal disorders
_____ disorders are mainly determined by alteration or MUTATION in the SINGLE GENE .
Mendelian
__disorders are transmitted to the offspring on the same lines as we have studied in the PRINCIPLE OF INHERITANCE .
Mendelian
The patter of inheritance of MENDELIAN disorders can be traced in a family by the ______ .
Pedigree analysis
Name some Mendelian disorders -
Haemophilia Cystic fibrosis Sickle -cell anaemia Colour blindness Phenylketonuria Thalassemia
Mendelian disorders may be _____ or _____ .
Dominance
Recessive
In _____disorders , the trait may also be linked to the sex-chromosome as in case of ____ .
Mendelian
Haemophilia
Haemophilia is a __trait and shows transmission from ___to _____ .
X-linked recessive
Carrier female
Male progeny
Myotonic dystrophy is a __trait .
Autosomal dominant - Mendelian
Colour blindness is a __disorder .
Sex-linked
Recessive
Colour blindness is due to _____ CONE of eye resulting in ______ .
Red or green
Failure to discriminate but red and green colour
Colour blindness is due to ___ in certain genes present not the X-chromo .
Mutation
Colour blindness occurs in about __% males and __% females .
8%
0.4%
The gene of colour blindness is ___ . Therefore it is suppressed in females .
Recessive
Haemophilia is a __ disease .
Sex-linked recessive
Haemophilia shows transmission from __To ____ .
Unaffected carrier female
Some male progeny
In haemophilia , a ___ that is a part of ____ involved in ____ is affected .
Single protein
Cascade of proteins
Clotting of blood
The possibility of a female being haemophilic is extremely rare becoz the -
Mother should be at least a carrier and father should be haemophilic
The family pedigree of queen victoria shows a number of _____ as she was a carrier of the disease .
Haemophilic descendants
What happens in haemophilia ?
A simple cut may result in non-stop bleeding
Sickle cell anaemia is an ___disease .
AUTOSOME linked recessive trait
When is sickle cell anaemia transmitted from parents to offspring ?
When both the parents are carrier for the gene (or heterozygous)
Sickle cell anaemia is controlled by _____alleles .
SINGLE PAIR of alleles
Which pair of allele controls sickle cell a ?
Hb-A
Hb-S
Out of the __possible genotypes , only the __indivisuals show the diseased phenotype for sickle cell .
3
Homozygous for Hb-S (HbS HbS)
__indivisuals are apparently unaffected but are carrier for sickle cell as there is ____% probability of transmission of the mutant gene to the progeny .
HbA HbS
50%
Sickle cell trait is exhibited by HbA HbS indivisuals. T/F
T
Sickle cell is caused by the substitution of ____ by ___ at the 6th position of ____ of _____molecule. .
Glutamic acid
Valine
Beta-globin chain
Haemoglobin molecule
The substitution of AMINO ACID in the GLOBIN PROTEIN results due to the _______ at the ____of the BETA GLOBIN GENE from ____to____ .(sickle cell )
Single base substitution
6th codon
GAG
GUG
In sickle cell , the mutant haemoglobin molecule undergoes _____ under ____causing a change in the shape of the RBC from biconcave disc to ELONGATED sickle like structure .
Polymerisation
Low O2 tension
Phenylketonuria is an __error of _____ .
Inborn
Metabolism
Phenylketonuria is an ___trait .
Autosomal recessive trait
What happens in phenylketonuria ?
The affected indivisual lacks an enzyme that converts PHENYLALANINE into TYROSINE
The affected indivisual in phenylketonuria lacks an enzyme that coverts __into ____ . As a result ___is accumulated and converted into ____ and _____ .
Phenylalanine Tyrosine Phenylalanine Phenylpyruvic acid Other derivatives
Accumulation of ___in the brain results in _____ in phenylketonuria .
Phenylpyruvic acid and other derivatives
Mental retardation
In phenylketonuria , ___is excreted through urine becoz of _____.
Phenylpyruvic acid
its Poor absorption by kidney
Thalassemia is n _____ disease .
AUTOSOME linked recessive blood
Thalassemia is transmitted from parents to offspring when -
Both partners are unaffected carrier for the gene ( or heterozygous)
Thalassemia disease is either due to _or _____ which ultimately results in _____ .
Mutation
Deletion
Reduced rate of synthesis of ONE of the globin chains (Alpha and beta chains ) that make up haemoglobin molecule
Reduced rate of synthesis of one of the globin chains that make up Hb in thalassemia causes -
Formation of abnormal Hb molecules resulting into anaemia
___ is characteristic of thalasemia disease .
Anaemia
Thalassemia can be classifies according to___
Which chain of Hb molecule is affected
In alpha -thalassemia production of ___ is affected while in beta-thalassemia, production of ___is affected .
Alpha-globin chain
Beta-globin chain
Alpha -thalassemia is controlled by __genes . name -
2 closely linked genes
HBA1 HBA2
The 2 closely __genes HBA1 and HBA2 are located on chromosome ___of each parent .
Linked
16
Alpha -thalassemia is observed due to _ or __ of _genes .
Deletion
Mutation
One or more of the 4 genes ( HBA1 HBA2 on both parents )
The more genes affected in alpha-thalassemia , ____ alpha-globin molecules are produced
Less
Beta-thalassemia is controlled by __genes . Name -
Single
HBB
Single gene HBB is located on chromosome __of each parent . Therefore beta-thalassemia occurs due to mutation of _genes .
11
One or both
That’s semi a is a __problem of synthesizing too few globin molecules while sickle cell is a ___problem of synthesizing an incorrectly functioning globin .
Quantitative
Qualitative
The chromosomal disorders are caused due to ____.
Absence or excess or abnormal arrangement of one or more chromosomes .
______duing cell division cycle results in gain or loss of a chromosome .
Failure of segregation of chromatids
Gain or loss of A CHROMOSOME is -
Aneuploidy .
Example of aneuploidy -
Down’s syndrome - gain in extra copy of chromosome 21
Turner’s syndrome- loss of an X-chromosome
___of cell division results in an INC in A WHOLE SET of chromo -
Failure of cytokinesis after telophase stage
Inc in a whole set of chromo is -
Polyploidy
Polyploidy is often seen in -
Plants
Cause of aneuploidy and polyploidy ?
aneuploidy - failure of segregation of chromatids - gain/loss of 1 chromo
Polyploidy -failure of cytokinesis - GAIN only of A set of chromo
Polyploidy results in a gain or loss of a whole set of chromo .T/F
F
Only gain
Chromosomal disorders may result due to ___Or _____ do chromo .
Monosomy
Trisomy
Name a few chromosomal disorders .
Down’s
Turner’s
Klinfelter’s
The cause of ___is the presence of an additional copy of chromo number 21 (trisomy of 21)
Down’s syn
Down’s syn was first described by ____ in __year .
Langdon down
1866
Downs syn is due to an additional copy of chromo __
21
The affected indivisual in downs is ___ with __head , _____tongue and ____ mouth .
Short statured
Small round head
Furrowed tongue
Partially open mouth
In downs syn , PALM is ______with characteristic _____ .
Broad
Crease
___,____and ____development is retarded in downs syn .
Physical
Psychomotor
Mental
____is caused due to additional copy of X-chromo .
Klinefelter’s
Klinefelters is due to an additional copy of __chromo resulting into a ___.
X-chromo
Karyotype of 47 , XXY
Klinfelter indivisual has an overall __Development , however , ___developemnt is also expressed .
Masculine
Feminine - development of breast .
While feminine character is observed in overall masculine klinfelter person . Name -
Development of breast
Gynaecomastia
_____is caused due to absence of one of the X-chromo .
Turners
Turners syn is caused due to ___of ____ . Karyotype of this indivisual is -
Absence
X-chromo
45 ,X0
Turners syn is seen in ____ and they are sterile as ___Are rudimentary .
Females
Ovaries
Features of turners .
Lack of sec sexual chars
Rudimentary ovaries
Characteristics of person with downs syn -
Flat back of head Broad flat fac Many loops on finger tips Big and wrinkled tongue Palm crease Congenital heart disease
