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Genetics Lecture IV Human Genetics Biology Standards Covered: Std 2f ~ students know the role of chromosomes in determining an individual’s sex Std 2f.

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Presentation on theme: "Genetics Lecture IV Human Genetics Biology Standards Covered: Std 2f ~ students know the role of chromosomes in determining an individual’s sex Std 2f."— Presentation transcript:

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2 Genetics Lecture IV Human Genetics Biology Standards Covered: Std 2f ~ students know the role of chromosomes in determining an individual’s sex Std 2f ~ students know the role of chromosomes in determining an individual’s sex Std 2g ~ students know how to predict the possible combinations of alleles in a zygote from the genetic makeup of the parents Std 2g ~ students know how to predict the possible combinations of alleles in a zygote from the genetic makeup of the parents Std 3c* ~ students know how to predict the probable mode of inheritance from a pedigree diagram showing phenotypes Std 3c* ~ students know how to predict the probable mode of inheritance from a pedigree diagram showing phenotypes

3 Exploring the Human Genome

4 Human Chromosomes Let’s Review: A diploid human cell contains 46 chromosomes A diploid human cell contains 46 chromosomes A haploid gamete or sex cell has 23 chromosomes A haploid gamete or sex cell has 23 chromosomes Chromosomes are a condensed form of DNA that carries all of the genetic information that makes up that organism Chromosomes are a condensed form of DNA that carries all of the genetic information that makes up that organism

5 Human Chromosomes Scientists have been analyzing our DNA to see what makes us human They take pictures of our DNA when it is condensed into the form of chromosomes After that they group the 23 pairs into matched pairs When chromosomes are arranged like this it is called karyotyping (karyotype)

6 Human Chromosomes Of the 46 chromosomes that make up each of our cells two of them are sex chromosomes It is our sex chromosomes that determine whether or not we are female or male Two X chromosomes and we are female (XX) Two X chromosomes and we are female (XX) One X and one Y and we are male (XY) One X and one Y and we are male (XY)

7 Sex determination XX Female Parent XY Male Parent X X XY XX Female XY Male XX Female XY Male

8 Human Chromosomes The other 44 chromosomes are known as autosomal chromosomes or autosomes This picture shows what type of cell? Sex cells or autosomal cells?

9 Human Traits Humans inherit genes according to the principles that Mendel came up with Both parents randomly assort their genes into their sex cells and the two sex cells are joined in fertilization Some traits are shown in the phenotype of the offspring while other traits are masked until further generations

10 A Human Pedigree A pedigree is a chart that shows how traits are passed from one generation to the next Spheres or circles represent females while boxes or squares represent males

11 A half-shaded circle or square represents a carrier, a heterozygous individual. Pedigrees illustrate inheritance

12 I II III IV Pedigrees illustrate inheritance A horizontal line connecting a circle and a square indicates that the individuals are parents, and a vertical line connects parents with their offspring.

13 Pedigrees illustrate inheritance Each horizontal row of circles and squares in a pedigree designates a generation, with the most recent generation shown at the bottom I II III IV

14 ? Pedigrees illustrate inheritance The generations are identified in sequence by Roman numerals, and each individual is given an Arabic number. I II III IV

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

16 Human Traits It can be quite difficult to trace an actual trait through generations of a family Some believe that you receive your eyes from one parent and ears from another Many traits, however, are considered polygenic ; Meaning: a trait that is controlled by many genes

17 Human Traits The second reason that it is difficult to determine where you receive your physical characteristics from is because only some of your genes are controlled by inheritance Many traits are strongly influenced by environmental, or non- genetic, factors Nutrition and exercise Nutrition and exercise Habitat and lifestyle Habitat and lifestyle In arctic foxes temperature has an effect on the expression of coat color.

18 Human Blood Group Genes Why is it important to know your blood type? If you receive a transfusion of the wrong blood type there is a very strong chance that you will die If you receive a transfusion of the wrong blood type there is a very strong chance that you will die Each person has a specific blood type and can receive donor blood specific to the type of blood that pumps through their veins & arteries Each person has a specific blood type and can receive donor blood specific to the type of blood that pumps through their veins & arteries

19 Human Blood Group Genes The ABO blood groups are the following: Type A, Type B, Type AB, and Type O Type A, Type B, Type AB, and Type O There are three alleles for the ABO blood group There are three alleles for the ABO blood group I A, I B, iI A, I B, i Phenotype (Blood Type) Genotype Antigen on Red Blood Cell Safe Transfusions ToFrom

20 Human Blood Group Genes  I A and I B are codominant  This means:  If you have both alleles you will have Type AB blood  If you have Type A or Type B with the i allele you will express the dominant trait of Type A or Type B Phenotype (Blood Type) Genotype Antigen on Red Blood Cell Safe Transfusions ToFrom

21 Type A Blood Type A blood is the result of the genotype I A I A or I A i The surface of all of the Type A blood molecules is the same throughout the body

22 Type B Blood Type B blood is the result of I B I B or I B i All of the blood in a Type B person has the same surface

23 Type AB Blood The only way to have Type AB blood is to have the alleles I A I B Because it has both surfaces it can accept donor blood from all blood types

24 Human Blood Group Genes  The i allele is recessive  This means:  If it is with any other allele it will be masked  If someone has both ii they will have Type O blood Phenotype (Blood Type) Genotype Antigen on Red Blood Cell Safe Transfusions ToFrom

25 Type O Blood With two recessive alleles ii you have the Blood Type O Type O blood has a smooth surface and because of that it is a universal donor

26 Human Blood Group Genes  Blood transfusions are specific  Type AB is the universal acceptor Type AB can ONLY donate to another Type AB !!  Type O is the universal donor  Type O can ONLY accept another Type O blood type Phenotype (Blood Type) Genotype Antigen on Red Blood Cell Safe Transfusions ToFrom

27 Human Blood Group Genes Human blood is governed by another gene as well The Rh Blood group only has two alleles Rh+ is dominant Rh+ is dominant Rh+ / Rh+ OR Rh+ / Rh- is positive Rh- is recessive Rh- is recessive ONLY Rh- / Rh- is a negative blood type


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