Lec 24 Flashcards
(32 cards)
Mendel used ?
Garden pea
Why pea plant ?
1- grow fast + large numbers
2- bigamous
3- easy cross pollination
4- has 7 unique traits
5- each trait has 2 contrasting phenotypes
What determines traits/phenotypes?
Genes
How are genetic traits transmitted?
1- blending ( rejected by Mendel )
2- particulate ( he addressed it ) : traits are carried on discrete particles/units/factors
Why are genetic disease more common in certain society?
Consanguinity/ inbreeding
How do genetic diseases spread ?
By carrier
How do we predict spread of genetic disease?
Punnett square
Mendelian laws :
1- proposed laws of inheritance
2- his laws are applicable in predicting inheritance of MONOGENIC HUMAN DISORDERS
3- father of genetics
4- simple genetics have no role on phenotypes
Pure / true breed plant “ HOMOZYGOUS “ :
Plant that retained a trait for multiple generations
Pea plant has —— pairs of chromosomes
7
Pea plant has —— traits
7
What are dominant traits of pea plant ?
1- purple flower
2- axial
3- yellow seeds
4- green pod
5- round seeds
6- inflated pod
7- tall
Monohybrid cross :
Cross between 2 plants each with a pure contrasting phenotype of a single trait
The product is a mono hybrid ( يظهر الصفة السائدة لكنه يحمل الصفة المتنحية )
What are recessive traits of pea plant ?
1- white flower
2- terminal
3- green seeds
4- yellow pod
5- wrinkle seed
6- constricted pod
7- short
Law of complete dominance
Only the dominant factor / allele / gene is expressed in F1
What happened to recessive phenotype in mono hybrid cross ?
It was suppressed by the dominant factor BUT It will appear in F2
Tall ( TT ) x Short ( tt ). P1
What is F1 ?
Tall ( Tt ) hybrid genotype
Each parent contributed 50% genetic material
Tall ( Tt ) x Tall ( Tt ) P2 / F1hybird
What is F2
- Tall ( TT ) homozygous 2. Short ( tt ) homozygous
3,4 . Tall ( Tt )
3:1 phenotype ratio ( التركيب الظاهري )
1:2:1 genotype ratio ( التركيب الجيني )
What is an assumption of F2 findings
1- A trait / phenotype is determined by a pair of factor ( alleles / genes / chromosomes )
Mendel rejected simple genetics which are :
Linkage
sex
environment
cross over
recombination
What are Mendel postulates from monohybird cross ?
1- in F1 -> law of complete dominance
§ the recessive factor expresses only in PURE/ HOMOZYGOUS condition ( tt )
2- in F2 -> a trait is determined by a pair of factor
3- in F2 -> law of segregation
§ during gamete formation, factors segregate and retain their identity , each haploid gamete receives 1 factor with equal likelihood
How do we calculate disease susceptibility & carrier frequency in a population ?
Hardy Weinberg equation
A fundamental tool in population genetics , derived by using Punnett square
Hardy Weinberg equation ( C+ c = 1 )
In a population, the frequency of a recessive allel ( c ) = 0.1 , what’s the frequency of : 1) carrier 2) disease
1) Cc carrier
C + c =1[ for allele frequency & to derive HW equation ]
C + 0.1 = 1
C = 0.9
2Cc = 2 x 0.9 x 0.1
2Cc = 0.18
2) HW equation for diseased cc
-Make Punnett square-> the result includes 2 Cc “ carriers “
- cc => c^2
= ( 0.1 )^2
= 0.01
