Dragonfly Chapter 14 The Human Genome Section 14

Dragonfly Chapter 14 The Human Genome

Section 14 -1: Human Heredity Key Concepts: How is sex determined? How do small changes in DNA Cause genetic disorders? I. Human Chromosomes A. Karyotype: A picture of chromosomes taken during mitosis and cut out and arranged into homologous pairs.

Diploid Cell: ____ of homologous chromosomes Two sets Human diploid cell has ____ chromosomes 46 arranged in ____ pairs 23 The 46 chromosomes contain 6 billion nucleotide pairs Mendelian genetics requires that organisms inherit a single copy of gene from each parent In humans, ________ (reproductive cells of the gametes egg and sperm) contain a single copy of each gene (one set of genetic information).

testes Gametes are formed in the _____ (sperm) and ovaries _____(egg) by meiosis. Each gamete contains 23 chromosomes (one set) or haploid number _________ (N) of chromosomes. Fertilization ________ requires the egg and the sperm to join and produce a _______ (fertilized egg) zygote that contains 46 chromosomes (two sets) or diploid number ___________ (2 N).

Humans have 46 total chromosomes 44 _______ follow regular Mendelian autosomes genetics 2 _________ (X and Y) are sex-linked sex chromosomes A. Pedigree Chart: A pedigree chart shows the _________ within a family and can be relationship genetic inheritance problems useful to help with _____________ within families. It is another _________ way to predict the outcome _____ of a particular cross and the genotype of the family members.

Figure 14 -3 A Pedigree Section 14 -1 Pedigree A circle represents a female. A horizontal line connecting a male and female represents a marriage. A half-shaded circle or square indicates that a person is a carrier of the trait. A completely shaded circle or square indicates that a person expresses the trait. A square represents a male. A vertical line and a bracket connect the parents to their children. A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.

Human Traits Phenotypes are determined by genotype as well as ________________. environmentally influenced ________________ on gene Environmental influences expression are not inherited, but genes are.

III. Human Genes The _________: Complete set of genetic human genome information Composed of about 30, 000 genes Blood Group Genes Human Blood comes in a variety of genetically determined blood groups There are many different types of blood groups but the ones associated with the ABO blood group and the Rh blood groups are best known.

Rh blood groups is controlled by single gene with ________. It is another antigen in blood, Two alleles first discovered in Rhesus monkeys. The arrangement of the alleles determines only _______ two positive possible types _______ (+) contains the antigen, or ______ (-) doesn’t contain the negative antigen. Positive is _______ over negative. dominant Rh-positive is identified with two genotypes: Rh+/Rh+ or Rh+/Rh. Rh-negative is identified with one genotype: Rh-/Rh

ABO Blood Groups: Discovered in 1900 by Karl Landsteiner. He realized that all blood is classified into four types: ____, and _____ due to A O B AB the presence of or absence of specific _____ antigens in the blood. o is Alleles IA and IB are _________ and i codominant A and IB ________ to both I recessive Antigens are ___________ used by chemical markers the immune system. When an unrecognized antigen is present an immune response takes place and the cells ______________. clump or agglutinate

Figure 14 -4 Blood Groups Blood Type and Antigen Interactions Section 14 -1 Phenotype (Blood Type Go to Section: Genotype Antigen on Red Blood Cell Safe Transfusions To From

B. Recessive Alleles: Trait controlled by a recessive allele. This results in the disorder being present ______________. only if both alleles are recessive • Examples include: PKU (Phenylketonuria), Tay Sachs disease and Cystic Fibrosis, Albinism, and Galactosemia (See chart on page 345)

C. Dominant Alleles: Traits controlled by a dominant allele. This results in the disorder being present when only one allele is present _____________. • Examples include: Achondroplasia (dwarfism), Hypercholesterolemia, and Huntington’s Disease

Section 14 -1 Autosomal Disorders Autosomol Disorders caused by Recessive alleles Dominant alleles Codominant alleles include Huntington’s disease Sickle cell disease Galactosemia Albinism Cystic fibrosis Phenylketonuria Tay-Sachs disease Achondroplasia Hypercholesterolemia

Huntington Disease: It is controlled by a _____________. single dominant allele The gene is located on Chromosome #4. Genetic degenerative disease that shows no symptoms until a person is in their __________. It progresses with thirties or forties gradual degeneration of their nervous system leading to loss of muscle control and mental function until death occurs.

Question? Would you want to know if you could potentially get Huntington’s disease when you are older? Would you want to know if you could pass the gene on to your offspring before you have children? A. Codominant Alleles: controlled by ____________________. two alleles that share dominance Sickle Cell Anemia is such a disorder. (This will be discussed in detail later)

IV. From Gene to Molecule The link between ___________ genetics and phenotype is not easily determined but for several diseases we have been able to make the connection. Cystic fibrosis Sickle cell disease For both _______ and ________ single gene a small change in the DNA of a _______ affects the ___________, causing a structure of a protein serious genetic disorder.

A. Cystic Fibrosis: (See figure 14 -8 p. 347) Cystic Fibrosis a. k. a. “CF” is a common genetic disease. It is most common in people of Northern European decent. It is a ____________ of a gene Recessive disease found on the # 7 chromosome and affects the_______________ digestive and respiratory systems

It is caused by the__________ in deletion of 3 bases the middle of a sequence for a protein and causes the protein to be _______ and abnormal doesn’t allow Chloride ions to transport across the membrane, as they should. This causes the cells in a person’s airways to be unable to transport chloride ions and become _________. clogged with mucus

Figure 14 -8 The Cause of Cystic Fibrosis Section 14 -1 Chromosome # 7 CFTR gene The most common allele that causes cystic fibrosis is missing 3 DNA bases. As a result, the amino acid phenylalanine is missing from the CFTR protein. Normal CFTR is a chloride ion channel in cell membranes. Abnormal CFTR cannot be transported to the cell membrane. The cells in the person’s airways are unable to transport chloride ions. As a result, the airways become clogged with a thick mucus.

B. Sickle Cell Anemia The patient’s blood cells were found to be irregularly shaped, __________, like a sickle and this is how the disease got its name. In normal red blood cells the __________ carries ______ oxygen hemoglobin molecule and distributes it around the body. In sickle cell disease, the red blood cells are sickle–shaped, causing the blood hemoglobin to no longer carry oxygen as well and ___________ disrupts the normal functioning of the bodies cells, tissues and organs

This person is deprived of oxygen and the result is physical weakness, and damage to the brain, heart, spleen. It may be fatal. The cause: A _________ in the DNA that single base codes for Hemoglobin polypeptides is changed. This substitutes Valine for glutamic acid. This change makes the hemoglobin less soluble in blood. This will cause the hemoglobin to come out of the blood and ________. This crystallize crystallization causes the ________ of sickle shape the blood cells and the medical consequences.

The genetics: The allele for sickle cell (HS) is ______ with the allele for normal hemoglobin codominant (HA). Heterozygotes (HS HA) are said to be ____ Sickle cell _____ and have some effects of the disorder carriers because they have both normal and sickle cell blood hemoglobin.

DNA normal hemoglobin CAC GTG GAC TGA GGA CTC Messenger RNA sequence GUG CAC CUG ACU CCU GAG Normal hemoglobin amino acid sequence Val – His – Leu – Thr – Pro – Glu… 1 2 3 4 5 6 7 … 146 DNA Sickle Cell Anemia CAC GTG GAC TGA GGA CAC CTC Messenger RNA sequence GUG CAC CUG ACU CCU GAG Val – His – Leu – Thr – Pro – – Glu… 1 2 3 4 5 6 7 … 146

The distribution: Sickle Cell anemia is most prevalent in people of _________. African descent 10% of African Americans and 40% of populations in Africa and Asia carry the gene for Sickle cell anemia. Why? The carriers for the disease have a __________, a dangerous disease caused resistance to Malaria by a blood parasite found in tropical areas of the world.

Sickle Cell Anemia is a _____ that has mutation provided an ______ in Malaria prone areas advantage and in these areas it is ____________ favored by natural selection and therefore Sickle Cell Anemia persists. HS HA HS HS HS HA HS HA HA HA

Section 14 -2: Human Chromosomes Key concepts: Why are sex-linked disorders more common in males than in females? What is nondisjunction, and what problems does it cause?

I. Human Genes and Chromosomes Human diploid cell contains ___________ of 6 billion base pairs DNA. All neatly packed into the 46 chromosomes. _________ of the DNA actually functions as Small part genes. Genes are located on the chromosomes and each gene occupies a ___________ on a chromosome. specific place Genes may exist in __________ (alleles) several forms Each chromosome contains ______ of the alleles for each of its genes one Chromosome #21 and 22 are the ______ of the human autosomes. These were the first two smallest chromosomes whose sequences had been determined.

Both also contain genes for some genetic disorders like ____________ Leukemia and Amyotrophic Lateral Sclerosis (ALS) ______________ We also discovered that there are many _____________ segments of DNA non-coding, repeating Human chromosomes also have ________ that can cross over just as we Linked genes saw in the fruit fly.

II. Sex-linked Genes Sex Chromosomes 1. ____________ are the ones that _____ in males and females differ 2. Chromosomes that are the ____ in male and same females = ________ autosomes 3. In humans: females = ____ and Males = ____ XY XX 4. The Y chromosome is smaller than the X

A. Sex Determination 1. Female _____ carry an X chromosome gametes 2. _____ gametes can carry either an X or Y Male (meiosis segregates the chromosomes; _______ 50% of the sperm carry X and ______ of the sperm carry Y) 3. In humans, _______________ males determine the sex of an offspring X Y Female: XX X XX XY male: XY X XX XY

In some animals such as birds, butterflies, and some fish, the female determines the sex differing because she has the _____ chromosomes. Sex-linked Genes 1. In addition to determining the sex of an individual, the sex chromosomes carry genes that __________ affect other traits.

Sex-linked Genetic Disorders May be on the X or Y chromosome, but usually on the X because the Y has very few genes. males Most often expressed in ______because they only have one X chromosome and thus all the alleles are expressed even if they are recessive. Colorblindness is a recessive disorder in which people can’t distinguish between certain colors. Red-green __________ colorblindness is most common. XC and Xc are ________ for normal and the alleles colorblind vision.

XC XC and XC Xc are both normal vision females. carrier for colorblindness XC Xc is a ____________ and can pass the gene on to her sons. Xc Xc is a colorblind female. XC Y is a normal male and Xc Y is a colorblind male. http: //www. toledo-bend. com/colorblind/Ishihara. html

Figure 14 -13 Colorblindness Section 14 -2 Father (normal vision) Colorblind Normal vision Male Female Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Mother (carrier) Go to Section:

Figure 14 -13 Colorblindness Section 14 -2 Father (normal vision) Colorblind Normal vision Male Female Daughter (normal vision) Son (normal vision) Daughter (carrier) Son (colorblind) Mother (carrier) Go to Section:

recessive sex-linked disorder Hemophilia is a _____________ in which one is unable to clot their blood. Also known as “bleeders disease”. Hemophilia is caused by a defect in a gene and the protein for normal blood clotting is missing.

Royal Family and Hemophilia

Muscular Dystrophy is another sex-linked recessive disease. Here the affected individual inherits a degenerative _____disorder. muscle The gene that codes for a _______ is muscle protein defective. They rarely live past early adulthood. Treatments are being explored that ______ replace the defective gene.

III. X-Chromosomes Inactivation Males survive with only one X chromosome so, what do females do with 2? They ______; shut one off it becomes inactive. This creates a dense region in the nucleus known as a _______. Barr body This is seen in coat color in cats. The cells will randomly shut off the coat color allele in one X chromosome and turn them off in the other X chromosome in other cells and this leads to some areas that are spotted orange and some spotted black, creating a tricolor cat, ____. This calico only happens in _____ because males only females have one X chromosome.

IV. Chromosomal Disorders Whole/sets of chromosome mutations 1. ________ = failure of homologous Nondisjunction chromosomes to separate normally during meiosis This results in a disorder of _________ chromosome number 2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome

Section 14 -2 Nondisjunction Homologous chromosomes fail to separate Meiosis I: Nondisjunction Go to Section: Meiosis II

Nondisjunction Section 14 -2 Homologous chromosomes fail to separate Meiosis I: Nondisjunction Go to Section: Meiosis II

Section 14 -2 Nondisjunction Homologous chromosomes fail to separate Meiosis I: Nondisjunction Go to Section: Meiosis II

Nondisjunction

2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome Nondisjunction disorders: Disorders in which the failure of ___________ chromosome separation during one of the stages of meiosis causes a gamete to have ________________. too few or too many chromosomes Nondisjunction can occur in ______________. autosomes or sex chromosomes

Down’s Syndrome: Down’s syndrome is an example of ______________, specifically nondisjunction of an autosome chromosome 21. In Down’s syndrome there is an ______ of extra copy chromosome 21 (trisomy 21). Doing a _______ (display of all the karyotype chromosomes in a cell nucleus) and looking at the chromosomes under a microscope detect the extra chromosome. Characteristics of Down’s syndrome include _________, physically challenged, facial mental retardation irregularities, and often heart defects.

Incidence of Down’s Syndrome and mother’s age

Turners Syndrome: Nondisjunction of the sex chromosomes in which a chromosome is missing. 45 XO They have the chromosome makeup of _____ where “O” represents the missing chromosome. This individual is female in appearance but does not develop the female sex organs during puberty and is sterile. ____.

Klinefelter’s Syndrome: Nondisjunction of the sex extra X chromosomes in which an ___________ is present. 47 XXY They have the chromosome makeup of ____. male They are ______ in appearance and are also sterile. May also be 48 XXXY or 49 XXXXY No nondisjunctions of the sex chromosomes have ever X chromosome produced and survived without an _______. This is because the X chromosome carries many genes essential for life.

• XXY condition • Results mainly from nondisjunction in mother (67%) • Phenotype is tall males –Sterile or nearly so –Feminized traits (sparse facial hair, somewhat enlarged breasts) –Treated with testosterone injections

Nondisjunction of Sex Chromosomes

The impact of the sex chromosome nondisjunction has led us to understand the importance of the ___________ Y chromosome in determination of sex of an individual. This has recently been determined to be true because the Y chromosome has been found to have a gene that turns on ___________ in the embryo male sexual development even if many X chromosomes are present.