Heredity / Genetics
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Heredity / Genetics. Early explanations for heredity? Gregor Mendel published 1865 Consequences of a monk proposing the nature of heredity? Early 1900’s accuracy recognized. Grew up on a farm Educated in mathematics (probability) & science. Why garden pea plant?. Explanation.

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Heredity genetics

Heredity / Genetics

Early explanations for heredity?

Gregor Mendel published 1865

Consequences of a monk proposing the nature of heredity?

Early 1900’s accuracy recognized

Grew up on a farm

Educated in mathematics (probability) & science

Why garden pea plant?


Heredity genetics

Explanation

Experimentation led to three basic conclusions:

inheritance of each trait is determined by "units" or "factors" (now called genes ) that are passed on to descendents unchanged

an individual inherits one such unit from each parent for each trait

that a trait may not show up in an individual but can still be passed on to the next generation.

Law of Segregation:

This says that of a pair of characteristics (e.g. blue and brown eye color) only one can be represented in a gamete.

Law of Independent Assortment

different pairs of alleles are passed to offspring independently of each other.  The result is that new combinations of genes present in neither parent are possible.


Heredity genetics

Gene for yellow seeds (Y), gene for green (y)

P1 = Pure bred cross - YY x yy


Heredity genetics

Essential Terms

  • Homozygous vs Heterozygous

  • Dominant vs Recessive

  • Phenotype vs Genotype

  • Ratio

  • Alele

  • Hybrid

  • Monohybrid Cross

  • Dihybrid Cross

  • P1. F1. F2

  • Punnet Square

  • Pedigree

  • Gamete

  • Probability

  • Product Rule


Heredity genetics

Human examples of Mendelian Traits

Listed below are human traits that reveal dominance & recessiveness -

All traits listed are the dominant phenotype

  • Tongue Curling

  • Widow’s Peak

  • Free Ear lobe

  • Brown Pigmented Iris

  • Hitch Hikers Thumb (45 degree angle)

  • Shorter Big Toe (shorter in length than second toe)

  • Mid Digital Hair

  • Freckles

  • Rh Factor

  • PTC taster

  • Left Thumb Over Top Right - (WhenInterlocking Fingers of both hands)

  • Short Palmar Muscle (Two tendons back of thumb to wrist is dominant, three is recessive)


Heredity genetics

What about combinations of characteristics?

Law of Independent Assortment

different pairs of alleles are passed to offspring independently of each other.  The result is that new combinations of genes present in neither parent are possible.

If we took two coins what is the probability of flipping one head and one tail? To determine this we must

realize that the outcome of one does not influence the outcome of the other. (Independent assortment).

Determine all of the possible outcomes

Head & Head = (1/2 x 1/2)

Head & Tail = 2(1/2 x 1/2)

Tail & Tail = (1/2 x 1/2)


Heredity genetics

When Mendel looked at combined characteristics:

Flower position (axial & terminal) and stem length (long & short)

Pure bred axial flower_round seed producing plant crossed with

pure bred terminal flower_wrinkled seed producing plant

AARR x aarr = all offspring AaRr

F1 all axial flower round seed producing plants (F1 hybrids)

F2 parents (AaRr x AaRr)

Gametes from AaRr (independent assortment)

AR , ar or Ar, aR

Axial_round = 9/16

Axial_wrinkled = 3/16

Terminal_round = 9/16

Terminal_wrinkled = 1/16


Heredity genetics

Product Rule:

The chance of two random events happening simultaneouslyis equal to the sum of their separate probablilities

Two coins both heads = 1/2 x 1/2 = 1/4

Pair of dice both coming up 6 = 1/6 x 1/6 = 1/36

One di and one coin coming up with a head and a six = 1/2 x 1/6 = 1/12

AaRr x AaRr the chance for getting AaRr = 1/2 x 1/2 = 1/4

Thc chance for getting AARr = ?

Phenotypic Ratio? (A_R_, A_rr, aaR_, aarr)

AaRrCcDd x AarrCcdd

AarrCcDd?

AARrCcDD?


Heredity genetics

Non-Mendelian patterns of inheritance

Incomplete Dominance:

Hybrids produce a trait that reveals a blend of both aleles

R = red W = white

RR = red

WW = White

RW = Pink

Co-Dominance

Hybrids reveals trait of both aleles

R = red W = white

RR = red

WW = White

RW = Roan (red & white colors)


Heredity genetics

Polygenic inheritance

Multiple pairs of genes all influencing one trait

Many pairs of genes influence the height of a human. Efficiency of the digestive system, circulatory system, and endocrine system - each being controlled by many pairs of genes - will all impact height.

Yao Ming 7’5” Earl Boykins 5’5”


Heredity genetics

Multiple Aleles

Traits in which within a population there exists more than two forms of a gene.

Human blood type - RBC surface proteins must be compatible when initiating a transfusion. Some people have A proteins on their RBC’s, others have B proteins., and others have neither.Within the human population there exists three forms of the gene that controls surface proteins on RBC’s.

Alele A (makes A proteins) Alele B (makes B proteins) Alele i (makes neither A or B)

  • Four main blood types: (phenotypes) A - B - AB - O

  • Genotypes:

  • AA, Ai - blood type A

  • BB, Bi - blood type B

  • AB - blood type AB

  • ii - blood type O

Ai x Bi ?


Heredity genetics

Sex Linkage

Most animal species have a special pair of chromosomes that determine gender. In humans 22 pairs of autosomes and 1 pair of sex chromosomes

Two types - X (large and has genes that control non gender related traits)

Y (small and only promotes the formation of male genitalia)

XX = female XY = male

Sex linked traits are traits controlled by genes on the X chromosome. Females have two, males have only one. Females can carry but not show defective sex linked traits. Males CAN NOT be carriers.

XX x XY


Heredity genetics

Duchene’s Muscular Dystrophy

Color Blindness

Hemophilia


Heredity genetics

Duchene’s Muscular Dystrophy

Color Blindness

Hemophilia


Heredity genetics

Duchene’s Muscular Dystrophy

Color Blindness

Hemophilia


Heredity genetics

Duchene’s Muscular Dystrophy

Color Blindness

Hemophilia


Heredity genetics

Duchene’s Muscular Dystrophy

Color Blindness

Hemophilia


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