Presentation on theme: "Cell division When one cell divides into 2 identical clones."— Presentation transcript:
1 Cell division When one cell divides into 2 identical clones. How then are we different?
2 Types 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.
3 Observable Patterns of Inheritance What you are is a result of genetic expressionHow Simple Traits Are Passed to the Next Generation
4 Genetic 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
5 Figure: 20-01Title:Important terms in genetics.Caption:
6 More 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
7 Table: 20-T01Title:Common terms in genetics.Caption:
8 More gene words Homozygous dominant: AA Heterozygous: Aa Homozygous recessive: aaGenotype: is the sum of all genesPhenotype: genes that are expressed
9 Mendels 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
10 Figure: 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.
11 The 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
13 Figure: 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.
14 The Punnett SquareProvides a simple way to view patters of inheritance for a single pair of alleles
15 The 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
16 The testcross Homozygous recessive a a A A a A a a a ? ? ? The old way to determine if someone is a heterozygoteAAaAaaaHeterozygote???
18 Figure: 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).
19 Figure: 20-05aTitle:Heterozygous parents and freckles.Caption:(a) Gamete formation by a person who is heterozygous for the freckle trait (Ff).
20 Independent 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
21 Variations 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
22 Height 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.
23 Chromosome variations The chromosomal basis of inheritance
24 Gene: unit of a heritable trait genes are located on chromosomes (locus)genes of different chromosomes are inherited independentlygenes on the same chromosome travel together
25 Autosomes 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
26 Karyotype:Is a visualization of the chromosomes where the chromosomes are lined up by size.Is used to determine if an abnormality occurred.
28 The 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
29 Figure: 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.
30 Sex 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
31 X 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
32 Chromosome Linkage What chromosome a gene is located on Chromosome #7 has CFX is hemophiliaY is TV clicker gene
33 Mutations 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
34 Genetic 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.
35 Human 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
36 Patterns Autosomal Inheritance Most of your genes have nothing to do with sex
37 Autosomal 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
38 Autosomal 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.
39 Patterns 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
40 Chromosomes can be abnormal DeletionDuplicationInsertionTranslocation
41 A 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.
43 What 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?
44 The 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.