Heredity & Genetics Part One: Mendel and the beginnings of Genetics: A.What are dominant & Recessive traits? B.How can you use a Punnett Square to predict the different Phenotypes and Genotypes of offspring? C.What is incomplete dominance?

Genetics parents inherit DNA I- Genetics: Similarities and differences among parents and offspring. It studies how offspring inherit characteristics from their parents and how DNA is involved.

Mendel A-Mendel: in 1866, this Austrian monk studied traits of pea pea plants. 1.Mendel studied traits one at a time. Each trait had two two forms. Height Height Tall Vs. Short Short. 2.Mendel grew short short and tall pea plants. 3.Mendel let these plants self-pollinate for several generations to get pure breed seeds. üSelf-pollinate = Pollination Pollination within one plant

pollen short 4.Mendel plants these seeds and lets them grow; then he takes the pollen from the tall pea plants and puts it on the short pea plants and vice- versa. Cross-pollination üThis is Cross-pollination= Take pollen from one plant and put it on another plant. Hybrids 5.The seeds Mendel collects from these plants are Hybrids. combination üHybrid = combination of two varieties of organisms.

6. Mendel plants the hybrid seeds to see if they will grow tall tall, short, or medium medium. They all grow tall tall.

self-pollinates hybrids 7.Mendel self-pollinates the hybrid for several generations, and plants the seeds from the hybrids. 3:1 ratio some grew tall some grew short.

8.Mendel concluded that the trait for tallness was visible visible and the trait for shortness was hidden hidden. Visible trait = dominant dominant, prevents the expression of recessive trait in organism. Hidden trait = recessive recessive.

B-What we learned from M MM Mendel. 1.From his work we know that traits (height) are determined by Genes Genes. Genes = a section of chromosomes chromosomes that determines a trait. { eye color, hair color, etc..} Two Two genes for every trait. Example tallness in pea plants if pure tall two tall genes, if short two short genes, if a hybrid one tall gene and one short gene. The different forms of a gene are ALLELES recessive {recessive & dominant dominant}

C- Using P PP Punnett Squares. 1.Genotype 1.Genotype = the genetic make-up of an organism. Homozygous: Homozygous: alleles of a gene are the same same. Heterozygous: Heterozygous: alleles of a gene are different different; one allele for tall one for short. Hybrids are heterozygous heterozygous. 2.Phenotype 2.Phenotype = What the organism looks like.

3.Punnett Squares: are used to predict the genotypes & phenotypes phenotypes of offspring. Symbols Symbols for different alleles of a gene. Dominant is capital capital and recessive recessive is lower case letter. Height = TT TT for dominant & tt tt for recessive. TT TT or tt tt= homozygous Tt = heterozygous heterozygous or hybrid.

4.Offspring receive one a aa allele for each t tt trait from each parent. 5.H eterozygous pass on either T or t.

D- Incomplete Dominance: Condition in which the two two alleles of a gene are both dominant dominant. 1-It produces a blended blended phenotype. This blended phenotype is the hybrid hybrid. Example: cross a pure red snapdragon snapdragon with a pure white snapdragon, and you get a pink snapdragon. RW RW is the hybrid note both are dominant.

Part Two Genes and Traits: A.In the nuclei of a human cell you find two sets of chromosomes chromosomes 23 pairs. This is a diploid diploid number of chromosomes.

1.One pair of the chromosomes comes from the father father the other set comes from the mother mother. 2.Genes are sections of DNA DNA, each human chromosome may contain 1,000’s 1,000’s of genes. 3.The way chromosomes pair pair up results in different genetic make-ups make-ups in the offspring.

B. B. Meiosis Meiosis: is the formation of sex cells or gametes gametes. 1.Eggs are produced in the female sex organ the ovaries ovaries, sperm is produced in the male sex organ the testes testes. 2.Meiosis produces sex cells with only one one set of chromosomes chromosomes these cells are monoploid monoploid. 3.In meiosis the chromosomes separate twice twice as do the cells.

4.Steps of Meiosis: a.1 st everything that occurs in M MM Mitosis happens with Meiosis. Except the nd time the chromosomes D DD DO NOT DOUBLE. b.Sometimes the twin chromosomes that are similar pair with each other. If they exchange DNA this is known as crossing over this increases the differences in the offspring compared to the parent.

3.At the end of meiosis we have cells with a monoploid monoploid number of chromosomes. HALF {HALF THAT OF PARENT CELL} 4.When the egg and sperm cells unite the two monoploid monoploid cells combine their DNA forming a diploid zygote zygote.

2n Diploid 4n n Monoploid

PART THREE I.How Sex is I II Inherited: Sex of an offspring is determined by a pair of c cc chromosomes. A.The m mm male body cell has X XX XY The f ff female body cell has X XX XX

1.During meiosis meiosis the eggs of the female receive an X chromosome. 2.During meiosis the sperm sperm cell of the male receive either X or YY.YY.

B.Twins: ONE ONE ZYGOTE SEX 1.IDENTICAL TWINS: ONE EGG IS FERTILIZED BY ONE SPERM. THE ZYGOTE SPLITS. ALWAYS THE SAME SEX. Sperm Egg Zygote Same Sex Always

2.F RATERNAL TWINS: T TT TWO EGGS AND TWO SPERM CELLS. THEY D DD DO N NN NOT CONTAIN THE SAME D DD DNA. CAN BE DIFFERENT SEX. 2 Egg 2 Sperms 2 Zygote

C. X-Linked Traits: are traits determined by genes on the x-chromosome.

1.Several diseases are more more common in males then in females. Women may not not be affected by the disease, but pass it on to their sons. These women are known as carriers carriers. X-chromosomes are larger larger so they carry more genes genes. The ability to see color color is on the x-chromosome x-chromosome.

2)X -chromosomes have genes that tell whether or not you see c cc color. (Red, G GG Green) Women are s ss seldom color-blind because the gene is a r rr recessive gene on the X-chromosome and they have two x-chromosomes. X ’ =recessive gene for c cc color- blindness

3)H emophilia: is another x-linked disease it is a blood disorder that prevents the blood from c cc clotting properly. X’ = recessive trait for hemophilia

IV.Source of Gene Variations: When cells divide each DNA molecule in the cell makes e ee exact copies of itself. But sometimes the cell makes a m mm mistake; bases may pair up i ii incorrectly. The codon are changed the a aa altered gene is passed on to the new cell.

A- Mutation Mutation is any permanent change in the DNA DNA of a cell. 1.Mutation increases increases with the exposure of DNA DNA to some chemicals chemicals ands radiation that damage damage the DNA molecule.

B.Chromosome Mutation: When a piece piece of chromosome breaks breaks and are rearranged rearranged or lost lost. During meiosis chromosomes mutation mutation may occur when chromosomes do not separate evenly evenly.

Dystrophy 1.Muscular Dystrophy= Weak muscles. Trisomy 21st chromosomes threechromosomes 2.Down Syndrome or Trisomy 21= is caused as a result of a sex cell having too many 21st chromosomes. The fertilized egg, contains three 21st chromosomes instead of two. newforms 3.Importance of Mutations= are a source of new traits or new forms of traits.