Early ideas about genetics Hippocrates Pangenesis Particles pangenes from each part of the body moved to the egg and sperm Changes in organisms over their lifetime would be passed on to offspring ID: 934063
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Slide1
Genetics
DNA & RNA
Intro to Genetics
Slide2Early ideas about geneticsHippocrates:
PangenesisParticles (pangenes) from each part of the body moved to the egg and spermChanges in organisms over their lifetime would be passed on to offspring Aristotle:Rejected HippocratesWhat was inherited was the potential to produce body features- not particles of the actual feature *How about weightlifting
?
Slide3Early ideas about genetics19th
century biologists offered “blending” hypothesisHereditary materials contributed by mother and father mix to form offspring and cannot be unmixedBlending of blue and yellow paintMake green
Slide4Gregor
Mendel
Mendel’s Peas
Genes & Dominance
Segregation
Slide5Mendel’s Peas
Genetics = the scientific
study of heredity
Gregor Mendel- The father of genetics
Slide6Slide7Mendel knew an important fact
of his
pea plants:
The flowers have both male & female reproductive parts.
Slide8True Breeding:
Natural process for pea plants
Slide9Remove immature stamens before they produce pollen!
Had to prevent self pollination!
Filial- “Son”
Slide10Did the recessive alleles disappear, or were they still present?
Slide11Biological characteristics are determined by genes.
(Genes are passed from parents to their offspring.)Mendel’s Results and Conclusions:
Slide12Mendel’s Results and Conclusions:
Some forms (alleles) of a gene may be dominant and others may be recessive.
Slide13In most sexually reproducing organisms, each adult has two copies of each gene—one from each parent. These genes are segregated/separated from each other when gametes are formed.
(Law of Segregation)Mendel’s Results and Conclusions:Homologous chromosomes separate from each other during Anaphase I of Meiosis
Slide14The alleles for different genes usually segregate independently of one another.
(Law of Independent Assortment)Mendel’s Results and Conclusions:
Slide15Terminology:
1.
Gene
- a section of DNA
that controls
a specific trait2.
Allele – alternative form of a GENE3. Trait—a characteristic of a species
determined by specific genes
Genes & Dominance
Slide16Dominant gene—the presence of this type of gene will mask/hide the other gene
Recessive gene—this gene is hidden by the other gene unless there are two copies of the recessive form.
Slide176
. Hybrid– offspring of crosses between parents with different traits7. Homozygous – Both pairs of genes for a specific trait are the same
8. Heterozygous
– Both pairs of genes are different
Genes & Dominance
Slide189. Genotype – the genetic makeup of
an organism (ie. AA, Aa, aa)
10. Ph
enotype – the physical appearance of an organism
(ie. Hair color, eye color, etc.)
Slide19Mendel observed a predictable ratio of traits in offspringIf you know the genotypes of the parents, you can predict the probability of the offspring receiving those traits
There is a big difference between probability and what actually happens (think of a coin toss).We can use Punnett squares to show the probable outcomes.
Slide20Punnett Squares!!!
= tool used to determine the probability of offspring of a cross between two parents
Slide21Mono
hybrid Crosses A cross between
individuals that involves
ONE pair of
contrasting traits
Slide22Probability
Segregation
The likely hood that a particular event will occur
Squares
Punnett
Probability predicts the average outcome of large numbers.
Past outcomes do not affect future outcomes
Slide23= DOMINANT
= recessive
Squares
Punnett
Punnett Squares
Can be used to predict & compare the genetic variations that will result from a cross
= DOMINANT
(capital letter)
= recessive
(lower case)
B
b
MonoHybrid
Cross
Slide24= DOMINANT
= recessive
Squares
Punnett
Can be used to predict & compare the genetic variations that will result from a cross
= DOMINANT
(capital letter)
= recessive
(lower case)
B
b
HOMOzygous
= organisms that have 2
IDENTICAL
alleles for the same trait
HETEROzygous
= organisms that have 2
DIFFERENT
alleles for the same trait
Punnett Squares
Slide25Slide26Test CrossTo determine the
GENOTYPE of an organism expressing the dominant phenotype. Testcross= a mating between an individual with an unknown genotype and an individual that is HOMOZYGOUS RECESSIVE. – Look at offspring to determine parent genotypeExample: Labrador Retriever
B- black furb= chocolate brown fur
Black lab X chocolate lab B___ X bb
Slide27TestcrossUsed to determine the genotype Mating between unknown genotype and homozygous recessive
Slide28Test Cross ExampleIn humans,
long eyelashes (E) is dominant short eyelashes (e). A man with long eyelashes marries a woman with short eyelashes and they have three children, two of whom have long eyelashes and one of whom has short eyelashes. Draw the Punnett squares that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children?
Slide29Independent Assortment Dihybrid Cross
Two-Factor CrossDo the genes that determine round/wrinkled have anything to do with seed color?
Slide30The alleles for different genes
usually segregate independentlyof one another. (Law of Independent Assortment)RRYY -> RY, RY, RY,RYrryy -> ry, ry, ry
, ry
Remember!!!
Slide31Patterns of Inheritance
SegregationSome alleles are neither dominant nor recessive, & many traits are controlled by multiple alleles or multiple genes
Slide32
One allele can completely hide the other (Mendel traits)
1. Complete Dominance
Slide33Incomplete Dominance
Slide34Codominance
Slide35Multiple Alleles
Slide36Multiple Alleles: Blood Type
Slide37Multiple Alleles and Codominance: Blood Type
Blood Groups: 3 Alleles = A (IA), B (IB), O (I)The four blood types areType A, Type B, Type AB, Type OA and B are
NOT dominant to each other, They are CodominantA and B are always
dominant to OAO= A blood typeBO= B blood type
Slide38Blood Typing Punnett SquareCross a woman Heterozygous for A-blood and a man with AB-blood
Parent Genotype:Genotypes:Phenotypes:
Slide39Polygenic Traits
Hair = 4 genes;
3, 6, 10, 18
Slide40Sex Linked- Genes on the X- chromosome
Only The X Chromosome carries genes. So, if a gene is on the X chromosome, a female would have to have TWO of those genes and the male would only have ONE.
Female with disorder
Female carrier
Male with Disorder
Slide41Sex Linked TraitsA genetic disorder that is found on the X chromosome
Females can be carriers and not have the disorderWould need both copies of the gene to have disorderMales express all sex linked genes because they only have one X chromosome If the X chromosome has it, they have itMales cannot be carriersExamples: Hemophilia and colorblindness
Slide42What do you see?
Slide43Sex Linked Punnett Square
A woman is heterozygous for normal visionShe marries a man who is colorblindWhat is the predicted colorblindness outcome for their children?N= Normal visionn= Colorblind Parent Genotype:Genotype:Phenoype:
Slide44Pedigree- A chart which shows the relationships within a familyPhenotypes are used to infer genotypes
Slide45PedigreesStudying genetic disorders in humans:It is unethical to use humans as test subjects (plus it would take too long to get the results), so one of the best ways to study human patterns of inheritance is to use a
PEDIGREE
Slide46DefinitionA chart which shows the relationship within a family
Slide47Pedigree Basics
= normal male= affected male
= normal female
= affected female
= marriage line
= children
= carrier female
Slide48Pedigrees can be used to predict if a trait is dominant, recessive, or sex-linked
Slide49Dominant
At least one parent must show the trait if it is dominant
Slide50Recessive
Recessive disorder can be passed from any combination of parents, as long as the dominant parent is heterozygous.
Slide51X-linked
Females can be carriersMore males may be affected
Slide52Sex Linked Pedigree
Slide53Genetic Disorders: Mutations
Single GeneMultifactorialChromosomalX-Linked
Slide54Genes that control human traits can be altered (mutated) and then be inherited by offspring
Genetic Traits and Disorders
Images from
: http://www.aldanaanatomy.com/category/skin/page/2
/, http
://www.eyesurgeonspc.com/lasik-rock-island/cataract_surgery_rock_island/cataract-surgery-rock-island.html, http://en.wikipedia.org/wiki/Polydactyly
Slide55Definition= a change in DNA sequence that affects genetic info
KEY = The result of
some
mutations are genetic disorders.
Mutation
Image from: http
://alsn.mda.org/news/c9orf72-mutation-most-common-cause-als-ftd-als-ftd
Slide56Four main
ways:Single geneMultifactorial Chromosomal abnormalityX-linked
How are disorders passed or inherited?
Slide57The problem trait is controlled by a
single gene and can be passed in a
dominant/recessive manner.
Slide58DD
= Dd
= dd =
aCHONDROPLASIA
(D)
~Bone growth abnormality
Slide59Cataracts (D)
~Dirty lens
Slide60Polydactyly
(D)~Multiple digits
Slide61Albino
(
r
)
~Lack of pigmentation
Slide62Sickle Cell Anemia
(r)
~Blood disorder
Slide63Result from mutations
in MULTIPLE genesEnvironmental
factors can also affect the
severity/onset of these disorders
Difficult to study and treat!
Slide64Autism
~Brain development disorder
impairments in social interaction & communication;
restricted interests and repetitive behavior
Slide65Cleft Palate
~the roof of the mouth (palate) has an opening (cleft) that may go through to the nasal cavity
Slide66In these disorders entire
chromosomes or large segments of chromosomes are missing, duplicated, or otherwise altered.
C. Chromosomal
Abnormality
Image from:
http://ghr.nlm.nih.gov/handbook/illustrations/chromosomaldeletion
Slide67Failure
of a chromosome to separate from its homologue during meiosisOne gamete receives an extra copy of a chromosome and the other gamete lacks the chromosome entirely
Ways chromosomal abnormality can occur:
Nondisjunction
Slide68DELETION
Ie. GCCATA GCATA
Slide69INSERTION
Ie. GCCATA GCCATCA
Slide70SUBSTITUTION
Ie. GCCATA CCCATA
Slide71DUPLICATION
Ie. GCCATA GCCGCCATA
Slide72Klinefelter’s
Syndrome
Extra
sex
chromosome
(
X)
Slide73Cri Du Chat
Slide74Disorders in which the mutation or errors are in genes found on th
e X chromosome. Examples are…1. Hemophilia
2.
Muscular Dystrophy3.
Colorblindness
More common in males
Females need 2 copies of the defective gene
Slide75Hemophilia
Bleeding disorder
Blood fails to clot properly
Slide76Hemophilia
Slide77Muscular Dystrophy
Slide78Color Blindness
Slide79Color Blindness
Achromacy
Normal
Deuteranopia
Tritanopia
Protanopia
Slide80Color Blindness