General Biology 1 Fall 2024 Past Paper PDF

General Biology 1 Fall 2024 Patterns of Inheritance – part 1 Prof : Dr. Vincent Gagnon Book Raven, Biology, 13th edition  Introduction to Genetics Study guide: Topic...

General Biology 1 Fall 2024 Patterns of Inheritance – part 1 Prof : Dr. Vincent Gagnon Book Raven, Biology, 13th edition  Introduction to Genetics Study guide: Topic References (13th Ed) State that human somatic cells contain 46 chromosomes. Differentiate between Section 13.1 autosomes and sex chromosomes. Explain sex determination in humans and other organisms. Explain dosage compensation where human X chromosomes are seen as Barr bodies Section 13.1, 51,1 when the nucleus is stained. Discuss the chromosomal theory, and how it was determined. Identify the individuals Section 13.2, Figure 13.2, responsible for developing the theory. Lab activities Discuss the difference between wild-type and mutant phenotypes and explain how Section 13.1, Figure 13.2, they can be used to understand inheritance patterns. Lab activities Identify selected human genetic disorders as the result of either: Recessive or Section 13.4, dominant genes, or whole chromosome abnormalities. Provide examples and state Table 13.2 the pertinent inheritance pattern responsible for each disease. Explain how humans can end up having a genome containing too many or too few chromosomes through a failure in meiosis (non-disjunction); and Identify autosomal Section 11.3, 13.4, Figure and sex chromosome abnormalities that are a result of non-disjunction. 13.13, 13.14, 13.15 Use correct notation to label the chromosomal abnormality as having too many or too few (2n + 1; 2n -1 for somatic cells; n-1; n+1 for gametes)) chromosomes Recognize that genes on the same chromosome can be linked, and may cross-over in Parts of p. 254 and 255 meiosis. Define karyotype, and describe the two techniques used to determine prenatal Section 13.4, Figure 13.16 karyotypes in humans: Amniocentesis, and chorionic villi sampling  Patterns of Inheritance Sex linkage and the chromosomal theory of inheritance Carl Correns – 1900 German botanist and geneticist, who rediscover Mendel’s work on heredity. First suggests central role for chromosomes. Walter Sutton – 1902 Carl Correns Chromosomal theory of inheritance. Based on observations that similar chromosomes paired with one another during meiosis (homologous chromosomes). Walter Sutton  Patterns of Inheritance Sex linkage and the chromosomal theory of inheritance Thomas Hunt Morgan – 1910 Was an American evolutionary biologist, geneticist, embryologist and science author. Won the Nobel Prize in Physiology or Medicine in 1933 for discoveries elucidating the role that the chromosome plays in heredity. Working with fruit fly, Drosophila melanogaster. Thomas Hunt Morgan Fly room Columbia University  Patterns of Inheritance Sex linkage and the chromosomal theory of inheritance Thomas Hunt Morgan – 1910 Discovered a mutant male fly with white eyes instead of red. Notation for allele of wildtype is the “+” symbol. For spontaneously or targeted mutant, “-” symbol is used. Thus a genotypes “-/-” for homozygous mutants, “+/-” for heterozygotes, and “+/+” for wildtypes.  Patterns of Inheritance Sex linkage and the chromosomal theory of inheritance Thomas Hunt Morgan – 1910 Discovered a mutant male fly with white eyes instead of red. Crossed the mutant male to a normal red-eyed female to test Mendelian inheritance. All F1 progeny red eyed, he concluded that the red allele was the dominant trait. This result for F1 progeny fit perfectly with Mendel model.  Patterns of Inheritance Sex linkage and the chromosomal theory of inheritance Thomas Hunt Morgan – 1910 Thing started to become interesting when Morgan crossed F1 females × F1 males. F2 generation contained ¾ red eyed and ¼ white- eyed flies. F2 followed the 3 red to 1 white eyed flies, as Mendel predicted. Strangely the only white eyed flies were male!  Patterns of Inheritance Sex linkage and the chromosomal theory of inheritance Thomas Hunt Morgan – 1910 Testcross of a F1 female with a white-eyed male showed that females and male were white-eyed. Morgan concluded that the eye color gene resides on the sex chromosomes (X chromosome). A trait determined by a gene on the X sex chromosomes is said to be sex-link.  Patterns of Inheritance Let talk about sex! Somatic cell: All cells of a multicellular organism that is not a sperm or an egg. They do cell division (mitosis). Diploid cells, 2 set of chromosomes in humans (2n = 46 chromosomes). Reproductive cell: Gametes are haploid cell, 1 set of chromosomes (n = 23 chromosomes), in humans (spermatozoa or eggs). Meiosis create those gametes (n) from diploid cell (2n). Offspring is a unique combination of genes from both parents.  Patterns of Inheritance Human karyotype 23 pairs of homologous chromosomes Pair of homologous chromosomes that are replicated centromere Sister chromatids Autosomes chromosomes: 23rd pair are the sex 1 to 22 pairs chromosomes  Patterns of Inheritance Sex chromosomes Y and X Typically, a female will have 23 homologous chromosomes whereas a male will have 22. That is because the sex chromosomes, X and Y, in males are not homologous they are called hemizygous.  Patterns of Inheritance Sex chromosomes According to species: Sex chromosomes repartition differ according to species. In human and Drosophile the male is hemizygous for the sex chromosomes (the chromosome are different). In birds the female is hemizygous for the sex chromosomes. In grasshopper the male lack the second sex chromosomes (Zero in the figure). In honeybee the female are diploid (2n) while the male are haploid (n).  Patterns of Inheritance Undifferentiated stage Sex determination in human The "default" setting in human embryonic development leads to female development.  Patterns of Inheritance Undifferentiated stage Sex determination in human The "default" setting in human embryonic development leads to female development. Some genes on the Y chromosome, notably the SRY gene, are responsible for the masculinization of genitalia and secondary sex organs. Male Female  Patterns of Inheritance The Barr bodies Although males have only one X chromosome and females have two, female cells do not produce twice the amount of the proteins encoded by genes on the X chromosome. Dosage compensation prevents doubling of sex- linked gene products. Inactivation* of one of the X chromosomes in female. Which of the two X is inactivated is done Female Male randomly throughout the body. The Barr body, inactivated X chromosome, is highly condensed, making it visible using staining and is located in nucleus attached to the nuclear membrane. Barr bodies First discovered by the Canadian *Not totally Murray Barr in 1948  Patterns of Inheritance The Barr bodies X chromosomes Allele for Best example is mosaic fur of the orange fur Early embryo: calico female cat. Allele for black fur The colour of the fur is coded on the X chromosomes and depending Cell division and which is activated (maternal X or X chromosome paternal X) the colour will change. inactivation Active X Active X Inactive X Black fur Orange fur  Patterns of Inheritance The Barr bodies  Patterns of Inheritance The Barr bodies Inactivation of one of the X chromosomes is also true for human female. If we were able to see it, female population would be stripped or spotted.  Patterns of Inheritance Definition: Inheritance is the passage of hereditary traits from one generation to the next. Chromosomes You get 23 chromosomes from your father and 23 chromosomes from your mother. You Pair of homologous chromosomes that are replicated Gene 1 centromere Gene 3 Gene 3 Sister Mother Father chromatids  Patterns of Inheritance Definition: Inheritance is the passage of hereditary traits from one generation to the next. Chromosomes You get 23 chromosomes from your father and 23 chromosomes from your mother. There are 223 (8 324 608) possible combinations of 23 chromosome pairs. So is there 1 chance in 8 324 608 that your bother or sister be identical to you???  Patterns of Inheritance Definition: Inheritance is the passage of hereditary traits from one generation to the next. Chromosomes You get 23 chromosomes from your father and 23 chromosomes from your mother. There are 223 (8 324 608) possible combinations of 23 chromosome pairs. So is there 1 chance in 8 324 608 that your bother or sister be identical to you??? NO…! Nature shuffler the genetic card way more!  Patterns of Inheritance Crossing over In prophase I of the meiosis, homologues chromosomes can physically exchange material by crossing over. This is done between homologues chromosomes (from both parents), not sister chromatids (DNA copy). There can be multiple cross over on one chromosome.  Patterns of Inheritance Crossing over The gamete with the cross over chromosome is now called the recombinant. The frequency for 2 particular alleles to cross over and change from one homologous chromosome to another is dependant its physical distance on the chromosome.  Patterns of Inheritance Genetic disorder display Sex linkage From ancient times, people have noted conditions that seem to affect males to a greater degree than females. This is due because the X and Y sex chromosomes are not homologous in male, thus a mutated recessive allele of a gene in the X of male is always express. While in female you have a backup X, thus only when the 2 alleles of the gene are mutated that you have an effect. To be noted, not all the gene on the sex chromosomes are related to sex characteristics.  Patterns of Inheritance Genetic disorder display Sex linkage  Patterns of Inheritance Genetic disorder display Sex linkage For example Red-green color blindness Red-green color blindness is one well-known condition that is more common in males because the gene affected is carried on the X chromosome An Ishihara color test plate. With properly configured computer displays, people with normal vision should see the number in green on an orange background. What number do you see ??  Patterns of Inheritance Genetic disorder display Sex linkage For example Red-green color blindness Red-green color blindness is one well-known condition that is more common in males because the gene affected is carried on the X chromosome An Ishihara color test plate. With properly configured computer displays, people with normal vision should see the number in green on an orange background. You should see the number " 74 “. Many people who are color blind see it as "71", and those with total color blindness may not see any numbers.  Patterns of Inheritance Genetic disorder display Sex linkage For example Red-green color blindness Red-green colorblindness involves loss of either red or green cones (photoreceptors)  Patterns of Inheritance Genetic disorder display Sex linkage For example Hemophilia Hemophilia is a disease that affects a single protein in a cascade of proteins involved in the formation of blood clots.  Patterns of Inheritance Genetic disorder display Sex linkage For example Hemophilia This form of hemophilia is caused by an X-linked recessive allele: women who are heterozygous for the allele are asymptomatic carriers, and men who receive an X chromosome with the recessive allele exhibit the disease.  Patterns of Inheritance Genetic disorder link to recessive somatic alleles For example Albinism Albinism is a disorder where recessive alleles are mutated and it’s characterized in humans by the complete or partial absence of pigment in the skin, hair and eyes. Long thought to be due to a single gene, albinism is now known to result from mutations in multiple genes; the common feature is the loss of pigment from hair, skin, and eyes Parents The genes are present Normal Normal Aa  Aa on the autosome chromosome, thus Sperm females and males are A a affected equally. Eggs Aa AA Normal A Normal (carrier) Aa Normal aa a Albino (carrier)  Patterns of Inheritance Genetic disorder link to nondisjunction of chromosome So far, we have been considering only single-gene disorders ( mutated allele), however there are also clinical syndromes due to changes in chromosome number. The failure of homologues or sister chromatids to separate properly during meiosis is called nondisjunction. Pair of homologous chromosomes that are replicated centromere Sister chromatids 23rd pair are the sex Autosomes chromosomes: chromosomes 1 to 22 pairs  Patterns of Inheritance Genetic disorder link to nondisjunction of chromosome  Patterns of Inheritance Genetic disorder link to nondisjunction of chromosome Aneuploidy: Individuals who have an anormal number of chromosomes.  Patterns of Inheritance Genetic disorder link to nondisjunction of the autosome Aneuploidy: Individuals who have an anormal number of chromosomes. Monosomic: Individuals who have lost one copy of an autosome. Generally do not survive embryonic development. Trisomies: Individuals who have gained an extra autosome. Extra autosomes for chromosomes 13, 15, 18, are viable at birth, but die within a few months. Extra autosomes for chromosomes 21 (Down syndrome) survive to adulthood. In these individuals, the maturation of the skeletal system is delayed, and have poor muscle tone. Their mental development is also affected.  Patterns of Inheritance Genetic disorder link to nondisjunction of chromosome Trisomies: The chance of having a child with Down syndrome is correlated with the age of the mother.  Patterns of Inheritance Genetic disorder Genetic test can be perform when a pregnancy is considered high risk. Amniocentesis: Removing a small sample of the amniotic fluid which contains fetal cells that can be grown in culture for analysis. Chorionic villi This less invasive method involves removing cells from the chorion, a sampling: membranous part of the placenta that nourishes the fetus. Amniocentesis Chorionic villi sampling  Patterns of Inheritance Genetic disorder link to nondisjunction of sex chromosome Problem is meiosis can lead to gamete with no sex chromosome or an extra amount. Various combinations of these gametes and normal gametes leads to zygotes with sex chromosome aneuploidies: XXX, XXY, XO, OY, and XYY.  Patterns of Inheritance Genetic disorder link to nondisjunction of sex chromosome Human Genetic Disorders (sex-linked) Problem is meiosis can lead to gamete with no sex chromosome or an extra amount. Nondisjunction of sex chromosomes can also occur resulting in too many sex chromosomes or not enough: - XXX = triple X females - XXY males = Klinefelter syndrome - XO females = Turner syndrome - OY = not viable (will not survive) - XYY males = Jacob syndrome  Patterns of Inheritance Genetic disorder link to nondisjunction of sex chromosome Human Genetic Disorders (sex-linked) XXX = triple X females - Generally appear normal both physically and mentally - Widely spaced eyes - Are fertile - Slight increased risk of mental retardation - Even women with 4+ X chromosomes are generally normal  Patterns of Inheritance Genetic disorder link to nondisjunction of sex chromosome Human Genetic Disorders (sex-linked) Klinefelter syndrome: Male XXY - Development of small testicles - Infertility - Lower levels of male sex hormones  Patterns of Inheritance Genetic disorder link to nondisjunction of sex chromosome Human Genetic Disorders (sex-linked) Turner syndrome: Female XO - Shorter then normal - Broad chest, low hairline and webbed necks - Dysfunction of the ovaries (sterile) - Puberty affected (may not undergo puberty) - Most suffer from heart disease  Patterns of Inheritance Genetic disorder link to nondisjunction of sex chromosome Human Genetic Disorders (sex-linked) Jacob syndrome: male XYY - Not many unusual physical differences (some slightly thinner and taller) - Normal fertility - Some have more severe acne than normal - Increased risk of learning and reading difficulties