Cytogenetics Lesson 4

7/28/2019 Cytogenetics Lesson 4

1/17

InheritanceandPedigrees


2/17

Genetics Terminology:Chromosomes & Genes

Genome - Completecomplement of anorganisms DNA.

Cellular DNA isorganized inChromosmes

Genes have specificplaces on chromosomes.

Image: Chromosome & gene, Graham Colm,National Human Genome Research Institute From the Virtual Cell Biology Classroom on ScienceProfOnline.com


3/17

Mendel's Laws

1. Law of Dominance

2. Law of Segregation

3. Law of Independent Assortment

Image: Gregor Mendel, Mendel's Principlesof Heredity: A Defense by Bateson, William. From the Virtual Cell Biology Classroom on ScienceProfOnline.com

(Johann)GregorMendel(1822-1864)Austrianmonk

whodiscoveredbasicprinciplesofhereditythrough

hisexperimentswithgardenpeasReceivedno

recognionforhisworkduringhislifeme


4/17

Mendels Law of DominanceIn a cross of parents that are pure for contrasting traits, only one form

of the trait will appear in the next generation.Offspring that are hybrid for a trait will have only the dominant trait inthe phenotype.

Mendels Law of Segregation- During the formation of gametes (eggs or sperm), the two alleles

(hereditary units) responsible for a trait separate from each other.- Alleles for a trait are then "recombined" at fertilization, producing

the genotype for the traits of the offspring.

Mendels Law of Independent Assortment- Alleles for differenttraits are distributed to sex cells (& offspring)

independently of one another.


5/17

AutosomalRecessive

AutosomalDominant

X-linkedrecessive

X-linkeddominantY-linked

Mitochondrial

WhatisMendelianInheritance?

MendelianInheritancereferstothetransmissionofinheritedtraitsfrom

generaontogeneraonthroughthetransmissionofgenes

Defini=onofterms:seenotes


6/17

______

Dominant & Recessive

Genotypes& Phenotypes____________ genotype:

Both recessive alleles must be present (rr).

___________ genotype:

At least one dominant allele is present (R-).

Character: Tongue Rolling

Being able to roll your tongue is a dominantphenotype.

Harry:Being able to roll your tongue is the dominant trait(phenotype).Q: How would we represent thegenotypeof hewashomozygous dominant?

Hermione:Not being able to roll your tongue is therecessive (phenotype).Q: What would be the recessive

genotype?

______

______

Q: Would Harriet be able to roll her tongue?

Genetics Terminology

From the Virtual Cell Biology Classroom on ScienceProfOnline.com


7/17

Autosomaldominantinheritancewhen

oneparentcarriestheautosomal

dominantfaultygenecopy.The

autosomaldominantfaultygenecopy

isrepresentedbyD;theworkingcopy

ofthegenebyd.

Autosomaldominantinheritancewhen

bothparentscarrytheautosomal

dominantfaultygenecopy.The

autosomaldominantfaultygenecopyis

representedbyD;theworkingcopyof

thegenebyd.


8/17

Parents

Gametes

Autosomaldominantinheritance


9/17

Parents

Gametes


At

conception


10/17

Parents

Gametes


At

conception


11/17

Parents

Gametes


At

conception


12/17

Parents

Gametes


At

conception


13/17

Parents

Gametes


Affected Affected Unaffected

At

conception


14/17


15/17


16/17

Autosomalrecessiveinheritancewhen

bothparentsareunaffectedgene=c

carriersforthecondi=on.Thefaulty

copyofthegenecontainingarecessive

muta=onisrepresentedbyr;the

workingcopyofthegenebyR.


onlyoneoftheparentsisanunaffectedgene=ccarrierforthecondi=on.The

faultycopyofthegenecontaininga

recessivemuta=onisrepresentedbyr;

theworkingcopyofthegenebyR


17/17


oneoftheparentsisanaffectedor

predisposedtodevelopthecondi6on.andtheotherparentisanunaffected

gene6ccarrierforthecondi6on.The

faultycopyofthegenecontaininga

recessivemuta6onisrepresentedbyr;

theworkingcopyofthegenebyR.


bothparentsareaffectedorpredisposed

todevelopthecondi6on.Thefaultycopyofthegenecontainingarecessive

muta6onisrepresentedbyr;the

workingcopyofthegenebyR.

Documents

Cytogenetics Lesson 4