Presentation on theme: "Cell division When one cell divides into 2 identical clones."— Presentation transcript:
1Cell division When one cell divides into 2 identical clones. How then are we different?
2Types of cell division Mitosis one mother cell into 2 daughter cells In growth, replacement, are identical to one anotherMeiosis one mother cell into 4 daughter cellsProduction of sperm (4) and egg (1+ 3 polar bodies)Will result in different individuals with differences.
3Observable Patterns of Inheritance What you are is a result of genetic expressionHow Simple Traits Are Passed to the Next Generation
4Genetic Terms: Genes: carry encoded information about specific traits Locus: the position of a gene on a chromosomeHomologous chromosome: two chromosomes that contain the same genes in diploid cells
5Figure: 20-01Title:Important terms in genetics.Caption:
6More genetic termsAlleles: various molecular forms of a gene for some trait. (same yet different)Homozygous: both alleles are the sameHeterozygous: the alleles differDominant: (A) allele that shows the phenotypeRecessive: (a) allele that is masked
7Table: 20-T01Title:Common terms in genetics.Caption:
8More gene words Homozygous dominant: AA Heterozygous: Aa Homozygous recessive: aaGenotype: is the sum of all genesPhenotype: genes that are expressed
9Mendels three basic rules Inheritance is controlled by discrete units (genes)Each diploid organism has two units for each trait (one from mom and one from dad)In parents different units assort independently into gametes (law of segregtion)if dad is heterozygous you have 50% probability of getting one or the other allele
10Figure: 20-03Title:Gamete formation and freckles.Caption:Gamete formation by a female who is homozygous dominant for freckles (FF) and a male who is homozygous recessive for no freckles (ff) and the heterozygous (Ff) individual resulting from the union of these gametes.
11The Pedigree Circles are females Boxes are males Empty boxes are normal (average)Filled boxes have the trait of interestA horizontal line indicates a mating or a brother sister relationship
13Figure: 20-07Title:The inheritance of cystic fibrosis is shown in this pedigree.Caption:A pedigree is constructed so that each generation occupies a different horizontal line, numbered from top to bottom with the most ancestral at the top. Males are indicated as squares, and females as circles. A horizontal line connects the partners in a marriage. An affected individual is indicated with a solid black symbol.
14The Punnett SquareProvides a simple way to view patters of inheritance for a single pair of alleles
15The Monohybrid cross A A A A A A A A A a a a Mating of two individuals with contrasting forms of one traitone of these traits will not show in the first generationPossible Male gametesAAAAAPossible Female gametesAAaaa
16The testcross Homozygous recessive a a A A a A a a a ? ? ? The old way to determine if someone is a heterozygoteAAaAaaaHeterozygote???
18Figure: 20-05bTitle:Heterozygous parents and freckles.Caption:(b) A Punnett square showing the probable outcome of a mating between two people who are heterozygous for the freckle trait (Ff).
19Figure: 20-05aTitle:Heterozygous parents and freckles.Caption:(a) Gamete formation by a person who is heterozygous for the freckle trait (Ff).
20Independent assortment When 2 different traits assort they do so without any affect on one another16 possible allele combinations exist 9:3:3:1 ratio in a dihybrid cross
21Variations on Mendelian Genetics Codominance: both alleles are expressed in heterozygotes like blood typeMultiple effects: one gene may have many phenotypes, cystic fibrosis, osteogenesis imperfectaPenetrance: phenotype depends on other genesPolygenic traits: result from 2 or more genes skin color, eye color, behavior, IQ
22Height controlled by 3 genes Figure: 20-10aTitle:Human height varies in a continuous manner.Caption:(a) One reason is that height is determined by more than one gene (polygenic inheritance). This figure shows the distribution of alleles for tallness in children of two parents of medium height, assuming that three genes are involved in the determination of height. The top line shows the parental genotypes, and the second line indicates the possible genotypes of the offspring. Alleles for tallness are indicated with dark squares.
23Chromosome variations The chromosomal basis of inheritance
24Gene: unit of a heritable trait genes are located on chromosomes (locus)genes of different chromosomes are inherited independentlygenes on the same chromosome travel together
25Autosomes and sex chromosomes Autosomes consistently 44 chromosomes of the same quantity and typeSex chromosomes: determine genderfemales XXmales XYall have 22 other chromosomes that are alike
26Karyotype:Is a visualization of the chromosomes where the chromosomes are lined up by size.Is used to determine if an abnormality occurred.
28The sex chromosomesOne of the few genes on the Y chromosome is the sry “make determining gene”Only one copy of the X chromosome is required by the cells, the extra copy in females is stored in a condensed formfemales are genetic mosaics because cell may express different X chromosomes
29Figure: 20-11Title:X-linked genes.Caption:Genes that are X linked have a different pattern of inheritance than do genes on autosomes, as seen in this cross between a carrier mother and a father who is normal for the trait. The recessive allele is indicated in red.
30Sex determination Gender is determined by the father’s sperm X bearing sperm fertilizes an egg, a female resultsY bearing sperm fertilizes an egg, a male resultsY has the male determining gene
31X chromosome inactivation in females Most or all of one X chromosome is switched off in early development of the femalethe female body is a mosaic of cells in which one or the other X chromosome is inactivated
32Chromosome Linkage What chromosome a gene is located on Chromosome #7 has CFX is hemophiliaY is TV clicker gene
33Mutations Are a change in the sequence of a gene (DNA is altered) can beNeutral - no change in the informationbeneficial - makes and organism betterharmful - can kill the organism
34Genetic testing before birth Figure: 20-14Title:Amniocentesis and chorionic villi sampling.Caption:Amniocentesis and chorionic villi sampling (CVS) are procedures available for prenatal genetic testing.
35Human Genetic analysis The pedigree, be able to write one outabnormal: genetic condition that is a deviation from the usual or average and is not life threateninggenetic disorder: conditions that cause medical problemsgenetic counseling: determining the probabilities and risks of having children
36Patterns Autosomal Inheritance Most of your genes have nothing to do with sex
37Autosomal Recessive Both parents must be a carrier only homozygous children are affected3:1 ratio of normal to affected childrenPhenylketonuria: mental retardationCystic fibrosis: build up of mucus in lungsTay-Sachs disease: lipid buildup in brain
38Autosomal dominant Inheritance Allele is expressed in each generationDwarfism: 4 feet in heightProgeria: rapid aging dies at age 10Huntington’s disease: degeneration of nervous system after age 40.
39Patterns of X linked inheritance X linked recessive occurs more in males than femalesHemophilia A, Duchenne muscular dystrophy, Color blindnessTesticular feminizing syndromemutation in the X chromosome on male results in defective receptors for the male sex hormonesembryo develops into an apparent female
40Chromosomes can be abnormal DeletionDuplicationInsertionTranslocation
41A woman with cystic fibrosis comes into your Genetic counseling clinic A woman with cystic fibrosis comes into your Genetic counseling clinic. She is going to marry her first cousin. What she wants to know that if they have children what is the probability that they will have a child with cystic fibrosis. Use your knowledge of genetics to give her an idea of the different probabilities.
43What does the filled figure mean What does the filled figure mean? What figure represents mails, which females. In what generation are the woman’s grandparents. Now that you know this information , what is the woman’s possibility of having a child with Cystic fibrosis? Using this example, explain why it is not a good idea for closely related individuals to have children together?
44The widow’s peak is a feature where the hairline dips down the forehead in a v like pattern. Look at 3 generations of your family Draw a pedigree and give the names of all the members of your family. Indicate weather they have a widows pear or if they have a straight hairline. Indicate weather you think the widows peak is dominant or recessive give your reasoning. If your family is all straight or widows peak describe what type of results you would need in order to determine if a trait is dominant or recessive.