Bio-Pac 06: Objective 11-14

Question 1

Objective 11. Explain the inheritance of sex-linked traits using hemophilia or color blindness as an example.

Answer 1

Sex-linked traits are traits (genes) that are linked to the X chromosome, meaning the hemophilia gene is on the X chromosome and not on the Y chromosome. Hemophilia is rare in women. The genotype for a normal female is XNXN for a normal female, XNXn for a carrier female, XnXn for a hemophilia female, XNY for a normal male, and for a hemophilia male the genotype is XnY. However there is no such thing as a male carrier. Inheritances of sex-linked traits are traits that are inherited because of sexual intercourse.

Question 2

Objective 12. Explain baldness as a sex-influenced trait.

Answer 2

Sex-influenced traits are when a trait is dominant in one sex while recessive in the other. For baldness it is dominant in males and recessive in females. So if baldness = B and normal hair= b, in men Bb is baldness and bb is normal hair, while Bb and bb is normal hair for women, and BB makes both sexes go bald.

Question 3

Objective 13. Describe the following non-disjunction related conditions: Klinefelter’s syndrome, Turner’s syndrome, and Down’s syndrome.

Answer 3

Down syndrome is trisomy in 21, meaning that a child gets an extra 21st chromosome. Turner’s syndrome is monosomy in the sex chromosome, meaning that a child has absence of one sex chromosome = XO (karyotype). These children are abnormally short, sterile females. Klinefelter’s syndrome is trisomy in the number of sex chromosomes, meaning that there is one extra chromosome (XXY). These are sterile, mentally retarded males.

Question 4

Objective 14. Explain the following types of mutations: point mutation, chromosome mutation, frameshift mutation, somatic mutation, and germ mutation.

Answer 4

Point mutation is a change in a single base pair in DNA. Chromosomal mutation is when some parts of chromosomes are broken off or lost during meiosis or mitosis, when a chromosome breaks and then rejoins incorrectly, or when the parts join backwards or to the wrong chromosome. Frameshift mutation is when a single base is added or deleted from DNA. Germ mutation occurs in gametes (egg or sperm). It can be passed on to the offspring, while somatic mutation is a mutation that occurs in body cells and cannot be passed onto the offspring.