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Chapter 11 Human Heredity.

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Presentation on theme: "Chapter 11 Human Heredity."— Presentation transcript:

1 Chapter 11 Human Heredity

2 11-1 “It runs in the family”
Many characteristics of human children are genetically determined Many human traits are inherited by the action of dominant and recessive allele genes, although other traits are determined through more complicated gene interactions

3 The Human Organism – A Review
Diploid cell – 2 sets of homologous chromosomes 46 chromosomes 23 pairs

4 6 billion nucleotide pairs
3,000 letters to a page – over 1 million pages

5 Gametes – sperm or egg Contain a single copy of a gene

6 Zygote – fertilized egg – 46 chromosomes
Formed when sperm and egg unite

7 Human Traits Phenotype is only partly determined by the genotype
Some traits are strongly influenced by environmental factors (non-genetic) Examples – exercise and nutrition

8 It is important to consider the influence of the environment on the expression of some genes, it must be understood that environmental effects on gene expression are not inherited;

9 Genes that are denied a proper environment in which to reach full expression in one generation can, in a proper environment, achieve full potential in a later generation (page 229)

10 11-2 The Inheritance of Human Traits
more than 3,000 human genes have been described

11 Human Blood Groups Multiple alleles – genes with more than two forms
Example – ABO and Rh blood groups * Remember – an organism can have two alleles only!

12 Blood Type – determined by the presence or absence of certain things in the blood
RBC (Red blood cell) – can carry two different antigens Antigens – molecules that can be recognized by the immune system

13 Genotypes and Phenotypes
ii IAIA or IAi IBIB or IBi IAIB Type O Type A Type B Type AB

14 Rh Blood Groups Rh antigen also on RBC Rh+ - have antigen (Dominant)
Rh_ - no antigen (Recessive)

15 Huntington’s Disease Caused by a single Dominant allele
Appears in 30’s or 40’s Progressive loss of muscle control and mental function  death Gene on chromosome 4

16 Sickle Cell Anemia Caused by a change in one of the polypeptides found in hemoglobin (carries oxygen in RBC) One nucleotide difference Codominant inheritance pattern – HAHS HA - normal allele HS – Sickle Cell allele

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18 Sickle Cell Anemia – common in people of African ancestry and from tropical regions
Carriers (heterozygous) of Sickle Cell trait (HAHS) resistant to malaria

19 Polygenic Traits Human traits that are controlled by a number of genes
Example – Height, Body weight, skin color Phenotypes seen in a range

20 Example – Skin Color 4 genes – some may have multiple alleles
Color is determined by the combination of genes Melanin – dark colored pigment The darker you are the more genes you have that code for the production of melanin

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22 11-3 Sex-Linked Inheritance
Genes on an X chromosome are inherited in a sex linked pattern

23 Nondisjunction Failure of chromosomes to separate properly during one of the stages of meiosis Turners Syndrome – 45X – female Klinefelters Syndrome – 47XXY - male

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25 Babies are not born without an X
X is essential for survival Sex is determined by the presence or absence of Y Y switches on a male pattern of growth

26 Sex-Linked Genetic Disorders
Gene for the trait is on the X or Y X has many genes – Y has few Defects easy to spot – appear more in males

27 Colorblindness Recessive X linked disorder Cannot distinguish colors
Dominant Gene – XC Recessive Gene - Xc

28 Carrier A heterozygous female – has the gene but does not express it – can pass it on to her children

29 Hemophilia Recessive X linked disorder Blood does not clot
XH – good gene Xh – hemophilia gene

30 Muscular Dystrophy Results in the progressive wasting away of muscle

31 Sex Influenced Traits A trait that is caused by a gene whose expression differs in males and females

32 Baldness A sex influenced trait Single gene – two alleles

33 Genotype Male Female BB Normal bb Bald Bb

34 11-4 Diagnosis of Genetic Disorders
Down’s Syndrome – Trisomy 21 Extra copy of the 21st chromosome Can be detected by microscopic examinations of chromosomes karyotype

35 Parental Diagnosis Amniocentesis – removes fluid from the sac around the baby The fluid can be used to grow cells and make a karyotype Chorionic Villus Biopsy – cells are removed from the embryo Faster than amnio.

36 CVB and Amnio make it possible to detect chromosomal abnormalities
Test for: biochemical abnormalities Presence of certain DNA sequences

37 We can detect over 100 disorders
Knowledge leads to choices and decisions Ethical Considerations

38 Genetic Engineering Biologists can engineer a set of genetic changes directly into an organisms DNA

39 Restriction Enzymes Proteins that cut genes at specific DNA sequences

40 Engineering New Organisms
Transgenic – organisms that contain foreign genes

41 Transgenic Bacteria put genes in bacteria and they make things humans need Ex. Growth hormone

42 Curing genetic diseases – 5% of babies in USA born with one
Decoding the human genome (determine the nucleotide sequence of about 3 billion nucleotides or about100,000 genes and to map their location on every chromosome) Personal Id Diagnosis of disease – 4,000 human genetic disorders

43 Genetic Counseling Karyotype DNA Fingerprint CVB Amniocentesis
Family History

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45 Pedigrees

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48 Huntington's disease pedigree

49 Which type of inheritance pattern is shown in the above pedigree?
What is individual II-4’s genotype? How many different genotypes are possible for individual III-2?

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