Chapter 27……..Human Genetics

 

Students should be able to:

 

·        Compare the chromosome number in body cells and sex cells

·        Describe methods that doctors use to study chromosomes of a fetus

·        Compare the chromosomes of males and females

·        Compare recessive and dominant traits with incomplete dominance

·        Describe different ways human traits can be inherited

·        Describe some genetic disorders in humans

·        Give examples of how genetic counseling can help families

 

Chapter Outline:

 

1.     Human body cells have 46 chromosomes in pairs 44 of the are called Autosomes and 2 are the Sex Chromosomes which are XX in females and XY in males. While sex cells have half the number which is 23 chromosomes and not paired

 

2.     Amniocentesis : a way to look at the chromosomes of the fetus by arranging them in pairs which called Karyotype

 

3.     Dominant and Recessive traits (check chapter 26)

 

4.     Incomplete dominance where both traits show their effect. For example sickle cell anemia where R is normal allele and R’ is sickle cell anemia so RR gives normal RBC , R’R’ gives sickle cell anemia, and RR’ gives both normal RBC and  sickle cell anemia

 

5.     Blood type inheritance : A gene for blood type A, B gene for blood type B,O or i gene for blood type O. Genes A and B show incomplete dominance ,but both are dominant over O so :

 

·        AA or AO result in blood type A

·        BB or BO result in blood type B

·        OO result in blood type O

 

6.     Genetic disorders that are sex linked that is on the X chromosomes that is females will have two alleles for the trait while males  will have only one allele .Examples of sex linked traits are color blindness and hemophilia  which are recessive sex linked traits

 

7.     Genetic disorder that are autosomal that  are on the autosomes and not affected by sex . Examples :

 

·        Dyslexia : word blindness ( Dominant trait)

·        Free earlobes ( Dominant trait)

·        Dimples curly hair ( Dominant trait)

·        Freckles ( Dominant trait)

·        Can roll the tongue ( Dominant trait)

·        Pointed hair in the middle ( Dominant trait)

·        Indentation in the middle of the chin ( Dominant trait)

·        Extra toe or finger ( Dominant trait)

·        Dark skin color ( Dominant trait)

 

8.     Pedigree : is used in genetic counseling to study how traits are passed along in a family

 

Study guide papers 157-162