FUNDAMENTALS OF GENETICSjessicadeckerscience.weebly.com/.../mendel_genetics_pdf.pdfGENETICS...

FUNDAMENTALS OF GENETICSChapter 9

Saturday, January 1, 2011

CH 9: FUNDAMENTALS OF GENETICS

Section 1: “Mendel’s Legacy”

Section 2: “Genetic Crosses”


MENDEL’S EXPERIMENTS

1800s: Gregor Mendel, a monk, started breeding experiments with pea plants

cross: mate or breed 2 individuals


WHY PEA PLANTS?

Pea plants are good for experiments because:

contrasting traits

self-pollinating (fertilize themselves)

grow easily


GENETICS VOCABULARYcharacters: physical features that are inherited (flower color)

trait: one of several possible forms of a character (ex: purple or white flowers)

hybrid: have some of both traits (F1 offspring)

True-breeding: always produce the same physical characteristics


MENDEL’S EXPERIMENTSStep 1: Allowed pea plants with each type of trait to self-pollinate; made sure they were true-breeding

Step 2: Crossed 2 true-breeding plants (P generation) with contrasting traits.

Step 3: Allowed F1 to self-pollinate and produce offspring (=F2 generation)


CHARACTERS STUDIEDFlower Color (P)

Seed Color (Y)

Seed Shape (R)

Pod Color (G)

Pod Shape (S)

Flower Position (M)

Plant Height (T)

For all 7 characters, Mendel found a 3:1 ratio of contrasting traits in the F2 generation


MENDEL’S THEORYMendelian Theory of Heredity: two of several versions of a gene combine and result in one of several possible traits.

allele: each version of a gene

DOMINANT: the allele that is fully expressed whenever it is present in an individual; capital letter

recessive: not expressed when the dominant allele is present; lowercase letter


MENDEL’S THEORYLaw of Segregation: when an organism produces gametes, each pair of alleles is separated and each gamete has an equal chance of receiving either one of the alleles

genotype: genetic makeup

phenotype: physical appearance

GENOTYPE DETERMINES PHENOTYPE!!


MENDEL’S THEORYhomozygous: 2 of the same alleles for a trait

heterozygous: 2 different alleles for the same trait; hybrid

Law of Independent Assortment: when gametes form, the alleles of each gene segregate independently

“linked” genes: genes located close together on a chromosome; rarely separate during crossing-over


CH 9: FUNDAMENTALS OF GENETICS

Section 1: “Mendel’s Legacy”

Section 2: “Genetic Crosses”


PROBABILITY

likelihood that an event will occur

(# one kind of possible outcome) (total # of all possible outcomes)

can be used to predict the probability that specific alleles will be passed on to offspring


MODELING MENDEL

Punnett square: models all of the possible genotypes that could result from a given cross.


BEYOND MENDELIAN HEREDITY

in nature, many traits do not work like Mendel suggested

polygenic inheritance: when several genes affect a character

height, skin color, and eye color in humans


Ch 12: Inheritance Patterns and Human Genetics

✤ Section 1: “Chromosomes and Inheritance”

✤ Section 2: “Human Genetics”


INCOMPLETE DOMINANCE

offspring will have a phenotype that is intermediate between traits of parents


MULTIPLE ALLELESgenes that have 3 or more possible alleles

codominance: both alleles for the same gene are fully expressed

Blood Type = A, B, O

IA = A

IB = B

i = O


PEDIGREEpedigree: family tree for genetics

genetic disorder: disease that can be inherited

carrier: has allele, but not disorder

sex-linked: on X or Y chromosome

Pedigrees help with:

sex-linkage

dominance

heterzygotes


P E D I G R E E O F R O YA L FA M I LYHemophilia (=the Royal Disease)


ENVIRONMENTAL EFFECTS

phenotype can be affected by conditions in the environment

nutrients: can affect height

temperature: affects color of Arctic Fox

Human Behavior


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