Genetics

Objectives d. Describe how flowering plants reproduce sexually. Identify chromosomes as cellular structures that occur in pairs that carry hereditary information in units called genes

Objectives b. Recognize and describe how when asexual reproduction occurs, the same genetic information found in the parent cell is copied and passed on to each new daughter cell c. Recognize and describe how when sexual reproduction occurs, genetic material from both parents is passed on and combined to form the genetic code for the new organism

Recognize and describe when asexual reproduction occurs, the daughter cell is identical to the parent cell b. Recognize and describe when sexual reproduction occurs, the offspring is not identical to either parent due to the combining of the different genetic codes contained in each sex cell

I. What is genetics? i. Genetics The study of heredity (how traits are passed from parents to offspring)

Think about the picture matching activity. Everyone in the class is alike, but different. How are we alike? How are we different? Click here and then on “Find out more about Heredity!Click here and then on “Find out more about Heredity!”

ii. Heredity How an organism passes traits from one generation to the next.

More definitions iii. Trait A characteristic or quality of an organism

iv. Traits that are advantageous are more likely to get passed on

The code for traits is contained in the nucleus of each cell of our body. Inside the nucleus are chromosomes which are made of DNA. This is the code to make you you. Cell Nucleus Chromosome DNA: One section of DNA is a gene

Defined: Tightly coiled DNA Form when cells divide –Chromosomes created for the new cells 2 Parts: –1) Chromatids: two identical parts of a chromosome –2) Centromere: Joins chromatids together

Chromosomes are very small. Here is what they look like when you see them through a microscope. Chromosome smear

One section of DNA is a gene

One Makes Two One makes two, asexual reproduction only one parent cell is needed for reproduction. The parent cell just simply divides producing newcells that are exact copies of the parent cell. Most single-celled organisms reproduce asexually and they do this by mitosis. Our body cells also are formed this way. 14

Sexual reproduction two parent cells join together to form a new individual. Parent cells, known as sex cells, are different from ordinary body cells. Human body cells have 46 chromosomes (or 23 pairs) The chromosomes in each pair are called homologous chromosomes. But human sex cells only have 23 chromosomes-half the usual number 15

Each parent donates one half of the homologous pair. This ensures that the offspring will have a normal number of chromosomes(46). 16

Sex chromosomes carry genes that determine whether the offspring is male or female. In humans, females have two X chromosomes (the matching pair), and males have one X chromosomes and one Y chromosome (the unmatched pair). 17

FemaleMale Images believed to be in the Public Domain Male Vs Female Chromosomes Females have 23 matching pairs. Males have 22 matching pairs of chromosomes.

1.Before a body cell divides it copies every one of the chromosomes. 2.When the body cell divides, each new body cell gets a copy of each chromosomes. 3.The new body cell is exactly like the original cell!! They have the same number and same type of chromosomes. Click here to see an animation of this.

OrganismChromosome numbers Human46 Chimpanzee48 House Mouse40 Maize20 © 2007 Paul Billiet ODWSODWS Normal Number of Body Cell Chromosomes

II. Who is Gregor Mendel?

An Augustinian monk who taught physics to high school students. As a young man worked as a gardener and continued to work with plants in his life as a teacher and as a monk.

II. Who is Gregor Mendel? i. Mendel became known as the father of Genetics for his work. ii. In the 1860s, Mendel studied variation using the traits of pea plants.

II. Who is Gregor Mendel iii. Plants a. A flower is a structure that contains a plant’s reproductive organs. 1. The stamen is the male organ that produces pollen (sperm).

II. Who is Gregor Mendel? 2, The pistil is the female organ that contains egg cells. b, During self- pollination, pollen is transferred to the top of the pistil (stigma) within the same plant this leads to fertilization (union of sperm and egg)

II. Who is Gregor Mendel? b. During cross-pollination, pollen is transferred to the stigma of another plant (fertilization)

II. Who is Gregor Mendel? iv. Mendel found patterns in the way traits were inherited. a. organisms contain two genes per trait (one from each parent)

II. Who is Gregor Mendel? b. Genes are units of heredity; determines traits in offspring. c.Dominant genes will mask (hide) other genes; “stronger” d.a recessive gene is hidden by a dominant gene; “weaker”

II. Who is Gregor Mendel? e. Purebred refers to an organism with a pair of the same genes for a given trait (either dominant or recessive); this is known as being homozygous.

II. Who is Gregor Mendel? e. Purebred refers to an organism with a pair of the same genes for a given trait (either dominant or recessive); this is known as being homozygous. f.Hybrid refers to an organism with two different genes for a trait (one dominant and one recessive); this is known as being heterozygous.

II. Who is Gregor Mendel? g.In genetics, each trait is noted by a single letter (i.e. “T” for tall plants)

II. Who is Gregor Mendel? g.In genetics, each gene is noted by a single letter (i.e. “T” for height) h.Capital letters are used to show which is the dominant allele (copy of the gene) 1. i.e. T = the tall allele (dominant) t = the short allele (recessive)

III. Are Genes Always Dominant and Recessive?

i.No, in some gene pairs, the genes are neither dominant nor recessive. During incomplete dominance, neither gene hides the other (each gene blends with the other).

IV. What are Phenotype and Genotype? i.Phenotype – the visible characteristics (traits).

Genotypes and Phenotypes Genotype: Indicates the alleles that the organism has inherited regarding a particular trait. Phenotype: The actual visible trait of the organism. Genotype Phenotype

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The resulting alleles show all the possible genotypes for the offspring. 39