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TRAITS • Living things inherit traits • Traits are the characteristics you have like hair color and eye color • Some traits are acquired, not inherited. • Some are a combination • What are some examples of acquired traits? HEREDITY • Heredity is the passing of genes from parents to offspring. • We get half our genes from our mom and half of them from our dad • Genes- is a segment of DNA at a specific location on chromosome. • We get a random mix of their genes. • “Father of Heredity” is Gregor Mendel GREGOR MENDEL • Mendel was born in Austria in 1822 Austrian Monk. Experimented with “pea plants”. Used pea plants because: They were available They reproduced quickly They showed obvious differences in the traits Understood that there was something that carried traits from one generation to the next- “FACTOR”. Mendel's Plant Breeding Experiments Gregor Mendel was one of the first to apply an experimental approach to the question of inheritance. For seven years, Mendel bred pea plants and recorded inheritance patterns in the offspring. Particulate Hypothesis of Inheritance Parents pass on to their offspring separate and distinct factors (today called genes) that are responsible for inherited traits. Mendel studies seven characteristics in the garden pea Mendel observed each trait MENDEL separately. Mendel started with truebreeding pea plants for each trait. A true breeding plant is one that always produces offspring with a particular trait. Example- a true breeding tall plant will always have tall offspring IDENTICAL VS. NOT IDENTICAL • Prokaryotes reproduce Asexually which means their offspring are genetically identical (the same) • Most Eukaryotes reproduce sexually which means they are a blending of traits. Each offspring gets ½ the genes from mom and ½ the genes from dad. GENES • DNA wraps around proteins and compacts (made smaller) to be made into chromosomes. • Genes are on chromosomes • A gene is a segment of DNA at a specific location on a chromosome that influences heredity characteristic. GENES • Each gene has a code for information that influences a trait. • Heredity is the passing of genes from parents to offspring. • Most traits are not coded for by just one gene. • Some characteristics are affected by many genes. CHROMOSOMES • In most Eukaryotes, cells contain pairs of chromosomes. • One chromosome in the pair comes from mom and one comes from dad. • Humans have 46 chromosomes • Each animal or plant has a specific # of chromosomes, Chimps have 48 and fruit flies have 8 or 4 pairs. SEX CHROMOSOMES • In humans, the sex chromosomes are called the X-chromosome and the Y chromosome • Females = XX • Males = XY HUMAN KARYOTYPE ALLELES • Alleles are alternate forms of the same gene. • For example, there is a gene for height in pea plants, but they have 2 forms- Tall and Short. • Alleles can be dominant or recessive. HOW ALLELES DIFFER recessive recessive Dominant - a term applied to the trait (allele) that is expressed regardless of the second allele. Recessive - a term applied to a trait that is only expressed when the second allele is the same (e.g. short plants are homozygous for the recessive allele). ALLELES INTERACT TO DETERMINE TRAITS WHO WAS THE FIRST PERSON TO STUDY HEREDITY? A. B. C. D. E. Watson and Crick Gregor Mendel Robert Hooke Louis Pasteur Charles Darwin HOW MANY CHROMOSOMES DO HUMAN HAVES? A. B. C. D. E. 23 38 56 44 46 GENES ARE LOCATED WHERE? A. On a chromosome B. In DNA C. Phenotype D. In our Allele’s E. Dominant WHAT ARE ALLELES? A. B. C. D. DNA Chromosomes Phenotype Different form of the same gene E. Dominant GIRLS HAVE WHAT KIND OF SEX CHROMOSOMES? A. XY B. XX PHENOTYPE • An organism’s phenotype describes the actual characteristics that can be observed. • Example: eye color, hair color, height, size of your feet. • Any observable trait is part of your phenotype. Blonde hair, green eyes GENOTYPE • Genotype is the name for the alleles an organism has. • Genotype is your genetic makeup. • Example: height in pea plants • Phenotype: Tall or Short • Genotype: Tall- TT or Tt Short- tt (which alleles the plant has) Genotypes RR Phenotypes RED Rr rr RED YELLOW TYPES OF GENES • Homozygous- means same genes TT or tt • You have 100% tall genes if you are a homozygous tall pea plant • Heterozygous- means different genes Tt, Aa • You have a mix of both types of genes DOMINANT GENES • Alleles (a form of a gene) can be dominant or recessive. • A dominant allele means it is always expressed if it is present. (but not always when multiple genes code for the same trait) • Example Pea Plants- the tall allele is dominant so if it is present the plant will always be tall. T= dominant • TT or Tt = tall plants RECESSIVE GENES • A recessive allele is one that is expressed only when two copies are present. • Example: In pea plants the short allele is recessive • tt = short plant TYPES OF DOMINANCE Complete dominance - two alleles code for a characteristic but only the dominant one is expressed (e.g. you could have alleles for both brown eyes and blue eyes but since brown eyes are dominant over blue eyes, you'll have brown eyes) Codominance - both alleles are expressed (e.g. a...I dunno - a dog has alleles for both red and black fur. If these alleles are codominant, that means the dog will have a mixture of black and red fur) Incomplete dominance - neither allele is dominant; the resultant phenotype is a mix of the two (red and white are incompletely dominant with flowers. So if a red and a white flower make more flowers, they would be pink) INCOMPLETE DOMINANCE CODOMINANCE COLOR BLINDNESS IN HUMANS: AN X-LINKED TRAIT Sex-Linked Traits: 1.Normal Color Vision: A: 29, B: 45, C: --, D: 26 2. Red-Green Color-Blind: A: 70, B: --, C: 5, D: -3.Red Color-blind: A: 70, B: --, C: 5, D: 6 4.Green Color-Blind: A: 70, B: --, C: 5, D: 2 PATTERNS OF HEREDITY • A punnett square illustrates how two parents’ alleles might combine in offspring. • Punnett squares show possible out comes for inheritance. PUNNETT SQUARES • Punned squares help scientists determine probabilities of a trait occurring. • A probability is the likelihood or chance of a specific outcome. • If you flip a penny what is the probability that it will land on heads? What is an organism’s phenotype? A. Their genes B. Their DNA C. It describes characteristics that can be observed D. Chromosomes E. Their personality What is an organism’s genotype? A. Their genetic makeup B. Their DNA C. It describes characteristics that can be observed D. Chromosomes E. Their personality WHICH GENES ARE HOMOZYGOUS? A. B. C. D. E. Tt Aa TT Hair color Zz A____illustrates how a parent’s alleles might combine? A. Cladogram B. Dichotomous Key C. Picture D. Diagram E. Punnett Square DNA • DNA is our genetic material that holds the information for our cells to function. • DNA is wrapped around proteins to make chromosomes. • Chromosomes hold our genes which influences hereditary characteristics. • A gene for height could have different forms (short, tall, etc). These forms are called alleles. DNA • DNA is in the shape of a double helix (twisted ladder). THE BASICS OF DNA • Each side of the ladder is made up of nucleic acids. • The backbone is a phosphate and a sugar • The rung of the ladder is the nitrogen base. Nucleotides O O -P O One deoxyribose together with its phosphate and base make a nucleotide. O O O -P O O O O -P O Nitrogenous base O O Phosphate C C O C Deoxyribose FOUR NITROGENOUS BASES DNA has four different bases: • • • • Cytosine Thymine Adenine Guanine C T A G TWO STRANDED DNA •Remember, DNA has two strands that fit together something like a zipper. IMPORTANT • A d e n i n e a n d Th y m i n e a lways j o i n t o ge t h e r A -- T • Cytosine and G u a n i n e a lways j o i n t o ge t h e r C -- G TYPES OF NITROGEN BASES A= adenine G= guanine C= cytosine T= thymine COPYING DNA Step 1- DNA unwinds and unzips Step 2- Once the molecule is separated it copies itself. The new strand of DNA has bases identical to the original DNA BY THE NUMBERS •Each cell has about 2 m of DNA. •The average human has 75 trillion cells. •The average human has enough DNA to go from the earth to the sun more than 400 times. •DNA has a diameter of only 0.000000002 m. The earth is 150 billion m or 93 million miles from the sun. WHAT SHAPE IS DNA? A. B. C. D. E. Circle Heart Double helix Regular ladder Twisted ladder WHAT PAIRS WITH ADENINE? A. B. C. D. E. Cytosine Thymine Guanine Nucleotides Adenine WHO DISCOVERED THE SHAPE OF DNA? A. B. C. D. E. Mendel Pastuer Hooke Darwin Watson and Crick WHAT PAIRS WITH CYTOSINE? A. B. C. D. E. Cytosine Thymine Guanine Nucleotides Adenine