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Introduction to Genetics. Genes= set of instructions for one protein; section of chromosome region of DNA that controls a hereditary characteristic (by making a particular PROTEIN!!). Introduction to Genetics. Trait= characteristic that is expressed and may vary from one individual to another

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introduction to genetics

Introduction to Genetics

Genes= set of instructions for one protein; section of chromosome

region of DNA that controls a hereditary characteristic (by making a particular PROTEIN!!)

introduction to genetics1
Introduction to Genetics
  • Trait= characteristic that is expressed and may vary from one individual to another
  • Heredity= passage of genetic information from parents to offspring
slide4
Heterozygous: Having two different alleles for a single trait.
  • Homozygous: Having identical alleles for a single trait.
  • Genotype:The genetic makeup of an organism
  • Phenotype: An organism\'s expressed physical traits.
slide10

The modern science of genetics was founded by an Austrian monk named Gregor Mendel.

  • Mendel was in charge of the monastery garden, where he was able to do the work that changed biology forever.
  • Mendel carried out his work with ordinary garden peas, partly because peas are small and easy to grow. A single pea plant can produce hundreds of offspring.
  • Today we call peas a “model system.”
slide11

Cross-pollination allowed Mendel to breed plants with traits different from those of their parents and then study the results.

slide16
Dominant Trait : the trait will always appear if the gene is present (Capital letter) (Dominant allele= dominant gene)
  • Recessive Trait: the trait that will appear if there are two copies of a gene…..otherwise this trait will be hidden by the dominant trait!! (lower case letter) (Recessive allele=recessive gene….the one that can be covered up)
slide17

Principle of Segregation

    • Allele pairs separate or segregate during formation of gametes (MEIOSIS) and recombine during fertilization
principle of independent assortment
Principle of Independent Assortment
  • Alleles for different traits are separated independently of each other
mendel s principles
Mendel’s Principles
  • The inheritance of biological characteristics is determined by individual units called genes.
  • When two or more forms (allele) of the gene for a single trait exist, some alleles may be dominant or recessive
  • In most sexually reproducing organisms, each adult has two copies of each gene– one from each parent. These genes segregate from each other when gametes are formed.
  • Alleles for different traits usually separate independently of each other
punnett squares
Punnett Squares
  • chart which shows/predicts all possible gene combinations in a cross of parents (whose genes are known).
  • Actually…..shows possible alleles parents may contribute!!
probability and punnett squares
Probability and Punnett squares
  • Why are the principles of probability able to be used to predict the outcome of genetic crosses?
  • Think about the “segregation of alleles”!!
slide27
Heterozygous: Having two different alleles for a single trait.
  • Homozygous: Having identical alleles for a single trait.
  • Genotype:The genetic makeup of an organism
  • Phenotype: An organism\'s expressed physical traits.
inheritance of traits
Inheritance of Traits
  • During fertilization…the male and female parents each contribute genetic information…to create the zygote
  • Zygote: fertilized egg; cell formed by union of gametes
slide29
Species chromosome number: the number of chromosomes normally in the body cell of the organism
    • Same from generation to generation
karyotype photograph chart of chromosomes in an organism arranged in pairs
Karyotype: photograph/chart of chromosomes in an organism arranged in pairs
  • Can tell gender….and certain diseases
genetics so far

Genetics so far……

Simple dominant/recessive one trait crosses!

Now……

Incomplete Dominance: a blending of traits; neither allele is completely dominant

Codominance: Each trait is expressed; both alleles are dominant

incomplete dominance
Incomplete Dominance
  • Alleles are neither dominant or recessive
  • The heterozygote phenotype is a blending (lies somewhere between the two)
codominance
Codominance
  • In a heterozygote…..both traits are expressed separately…both are dominant
  • Example…..
codominance1
Codominance

Codominance helps to explain the inheritance of Human Blood Types

human blood typing
Human Blood Typing
  • Blood type is determined by antigen found on red blood cell
codominance and multiple alleles
Codominance and Multiple Alleles!!
  • There are more than two alleles (gene possibilities) (Multiple Alleles)
  • A (I A), B (IB), and O(i)
  • Both A and B are dominant(Codominant)
  • O is recessive
slide45

If an antigen is introduced to a person that cannot recognize it…they will make antibodies against it…..and attack it!

  • This will cause the blood to clump…clots...
  • So blood types need to be matched
  • If the person can recognize it…they can have it!!
pedigree chart

Pedigree Chart

Traces the pattern of inheritance through many generations

slide52

Female

  • Affected Female
  • Male
  • Affected male
human genetic diseases
Human Genetic Diseases
  • PKU: an enzyme needed to metabolize a particular amino acid is absent; if not detected early mental retardation may occur
  • Sickle-cell Anemia: formation of abnormal hemoglobin; makes RBC’s fragile and gives them a sickle shape
  • Tay-Sachs: an enzyme is not synthesized and that allows for an accumulation of a fatty material on nervous tissue; fatal disease
  • Cystic Fibrosis: a non-secretion of digestive enzymes; allows for a abnormal build-up of mucus (recessive) (chromosome 7)
  • Specific disorders
  • Information from Genome Project
slide58

Albinism: inability to produce melanin (recessive)

  • Huntington\'s Disease: adults lose muscle control, convulsions, nervous degeneration causes death (chromosome 4) (dominant)
  • Polydactyly: dominant disorder that causes extra fingers and toes
sex determination
Sex determination
  • Sex chromosomes: 1 pair of chromosomes…..responsible for determining gender (X or Y)
  • Autosomes: the other 22 pairs of chromosomes ( not sex)
slide60
Sex chromosomes are represented by X and Y
  • Egg cells carry only X chromosomes
  • Sperm cells carry either an X or Y
  • At fertilization: XX=female
          • XY=male
sex linked inheritance
Sex-Linked Inheritance
  • Several genes found on X chromosome but not on Y….X is larger!!
  • Sometimes these genes on the X carry genetic diseases and are called sex-linked genes
  • Usually recessive
  • Females who have one recessive gene and one normal gene are called carriers
polygenic inheritance
Polygenic Inheritance
  • Traits controlled by more than one gene pair (allele)
  • Most human traits are polygenic
    • Skin color, height

Resulting phenotypes show

range of differences!!

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