bio principles of inheritance and variation

hereditary

science that deals with the principles of how characters are transmitted from parent to offspring

reason for mendel using garden pea

PISCUM SATIVUM is used because

-short life span

self fertilisation can be controlled

large number of contrasting characters

structurally suitable for cross pollination

bisexual

reasons for mendels success

utmost care

took notes and analysed statistically

emasculation and bagging to prevent self pollination

started experiments with pure line character plants

kept plants with different characters separately to prevent intermingling

monohybrid cross explanation

pure line cross pollination, show diagram

conclusion- disappearance of dwrf in f1 but the reappearence in F2 formed mendles law of dominance

alleles

each genetic character is governed by factors called alleles

law of dominance

Flashcard:

Term: Law of Dominance

Definition: In geneticsthe law states that when two different alleles are present in an organism, one allele can mask the expression of the other, resulting in the dominant trait being expressed in the phenotype.

the character that appears in F1 generation is

DOMINANT

law of segregation

Flashcard Term: Law of Segregation

Definition: The principle stating that during the formation of gametes, the two alleles for a trait separate so that each gamete carries only one allele for each gene. This means that offspring inherit one allele from each parent, ensuring genetic diversity.

from a pair of contrasting characters only one is present in a single gamete , and one character is dominant and other is recessive in F1 AND F2 these characters are segregated in the ration 3:1

what helped mendel create law of dominance and segregation

MONOHYBRID CROSS

genotype

genetic makeup

phenotype

Term: Phenotype

Definition: The observable physical and physiological traits of an organism

conclusion of dihybrid cross

the genetic inheritance of two contrasting characters in independant of each other, the genes for two characters do not influence each other

MODIFICATION- as long as they are present on different homologous chromosomes.

law of independent assortment

when there are two pairs of contrasting characters the distribution of each pair to a gamete is independent to the distribution of the other pair of characters

test cross does what

determines genetic nature of an individual

dominant phenotype may be homozygous or heterozygous

in test cross can dominant phenotype be hetero or homo

BOTh

test cross working

unknown geneotypes are crossed with HOMOZYGOUS RECESSIVE

if reslults of test cross show all dominant phenotypes ( homo and hetero)

the geneotype is HOMOZYGOUS DOMINANT

if results show equal dominant and recessive phenotypic ratio

HETEROZYGOUS DOMINANT

no of gemetes

2 to the power n

( n= heterozygous pairs )

no of phenotypes in selfing F2

2 to the power n

no of genotypes in selfing F2

3 to the power n

no of zygotes formed from F2 selfing

4 TO THE POWER N

biological imp of mendels laws

plant breeders- to produce crops with desirable characters

animal breeders to promote quality cattle and poultry

remove defective characters from the human race and promote useful genes in the human population

laif the foundation for modern molecular genetics

incomplete dominance

SNAP DRAGON

pure red and pure white flowers crossed whoch in F1 gave all pink flowers goes against mendels first principle,

IN f2 RATIO was 1:2:1 which goes against law 2

• in incomplete dominance , domiance is not perfect or complete , alleles interact with one another which causes causes bleeding characteristics

codominace

Flashcard:

Term: Codominance

Definition: A genetic scenario in which both alleles in a heterozygous organism are fully expressed, resulting in a phenotype that displays characteristics of both alleles.

BLOOD GROUP a and b when separate show separately but together in heterozygous ( present in same allele) become BLOOD GROUO AB

homozygous parent produces gametes that are

SIMILAR

multiple alleles

Front:What is a genetic scenario involving more than two alternative forms of a gene?

Back:This concept refers to a situation where a single gene has more than two possible alleles, leading to a variety of phenotypes. Common examples include blood type in humans,

inheitance of abo blood group

goverened by 3 alleles Ia Ib and i

IA IB and i result in

4 blood groups

A,B ,AB AND O

IA AND IB ARE

codominant

i allele is

recessive to both IA AND IB

geneotypes for A,B, AB AND O

IA IA, IA i

IB IB , IB i

IA IB

ii

no . of genotypes when allele is given

n(n+1)/2

n= alleles

PLEIOTROPIC GENE

when one gence influences the expression of more than one character

pku

phenylketonuria

mutation in the gene coding for enzyme phenlyalanine hydroxylase.

enzyme phenylallanine hydroxylase converts phenylalanine to tryrosine.

in absence of this enzyme- phenylallanine accumulates in blood and results in mental retardation

tyrosine precursor to melanin so with the mutation melanin cannot be synthasised= albinism

starch synthesis as an example of pleitropy

one gene is controlled by two alleles - B and b

gene B is used to dteremine both shape and size see book page 189

mullato

intermediate skin colour

polygenic inheritance

quantity of genes determine nature of inheritance

chromosomal theory of inheritance

parallelism between gene and chromosomes

both are found in pairs

both are separated after gametogenesis

both return to their paired state after fertilisation

features of chromosomal theory

• after fertilistaion diploid zygote is formed , this zygote containeschromosomes shares by maternal and paternal parent, zygote get a chromosome of the each type from both set of parents , this set of both = HOMOLOGOUS CHROMOSOME

• during gamete formation g=homolgous chromosome is separated therefore gene is also separated

• each chromosome carries genes

• chromosomes remain unique and structurally unique throughoutr outr lives

why did morgan use fruit flies

• good sexual dimorphism

• short life span

• one mating mutiple offspring

• recognisable clear cut characters

allosome

FlashcardDefinition: A type of chromosome that determines the sex of an organism, differing in shape or size between sexes. In humans, these are the X and Y chromosomes, with females typically having two of the same kind and males having one of each. They play a crucial role in sexual reproduction and inheritance patterns.

autosome

chromosomes other than sex chromosome 22 pairs

sex determination

determining sex

homogametic female sex determination

grass hopper 2A+ XX AND 2A+XO

human 2A+ XX AND 2A + XY

homogametic male

birds 2A+ZW AND 2A+ZZ

SEX DETERMINATION IN HINEY BEE

VERY IMPORTANT

linkage

genes that are together during the course of inheritance

significance of linkage

preserves parental traits

• reduces variability

• gene location

• prevents recombination

crossing over and significance

exchange of chromosomal parts between non sister chromatids or homologous chromosomes

variation

chromosomal maps

genes linear manner

evolution

chromosomal abberations

affect number and structure of chromosomes

euploidy

monoploidy

polyploidy

autoplooidy

allopolyploids

autoalloploidyploids

colour blindness for blue colour is

AUTOSOMAL

red , green, blue blindness names

protanopia , beuteranopia tritanopia

klinefelters, turners , down syndrome

2a+ XXY , 2A+ XO , 21ST trisomy

hameophilia more likely in males

x linked femals have two , chnaces of both being affected are lessers