Chapter 4

• What is the mechanism by which sex is established?

  sex-determination
• In humans, females inherit an XX pair of sex chromosomes, while males inherit an XY pair.
• The Y chromosome contains genes that determine maleness, while the X chromosome does not have such genes.
• In the XX-XO mechanism of sex determination, females have two X chromosomes (XX) and males have one X chromosome (XO)
• What results in the male sexual phenotype in humans?

  the presence of the SRY gene on the Y chromosome
• Humans have only one X chromosome and are sterile. Which condition is this?

  Turner syndrome
• Sponges can produce sperm and eggs in a single organism. Which term describes the sex system of the organism?

  Monoecious
• Y-linked traits are passed down to a son by his father
• In organisms with the ZZ-ZW sex determining system, how can a female inherit her w chromosomes?

  Her mother’s mother
• In XX-XY sex determination, males pass X-linked genes to their daughters but never to their sons or their sons’ descendants.
• What are some uses for the PCR test?

  Paternity test or dna at crime scenes
• What does PCR stand for?

  Polymerase Chain Reaction
• If DNA is amplified, it can be proven if it is is a genetically modified organism.
• Primer is short dna and single strand
• 2 primers are used to eliminate the area needed in a PCR test.
• 5’ to 3’
• Non-recombinance are gametes that don’t cross over
• Non-disjunction occurs in meiosis 1 when 2 chromosomes go on one side
• Non-disjunction occurs in meiosis 2 when chromatids don’t separate
• Males produce small gametes and females produce relatively large gametes
• Hermaphroditism is when both sexes are present in the same organism
• Organisms that bear both male and female reproductive structures are said to be monoecious
• Organisms that bear either male and female reproductive structures are said to be dioecious
• Non sex chromosomes are called autosomes
• Heterogametic sex is when the gametes are different in type
• Homogametic sex is when gametes are the same with respect to the sex chromosomes
• In the ZZ-Zw sex determining system, female is heterogametic and the male is homogametic.
• After meiosis, half of the female eggs have a Z chromosomes and the other half a W chromosome.
• All sperm contain a single Z chromosome in the ZZ-ZW sex determining system
• Genic sex determination is when genotypes at one or more loci determine the sex of an individual
• An X:A ratio between 1.0 and 0.5 is considered intersex.
• Intersex is a mixture of female and male characteristics
• People who have Turner syndrome have only one X chromosome.
• People with Turner syndrom have underdeveloped secondary sex ccharacteristics, and are infertile
• People who have Klinefelter syndrome have cells with one or more Y chromosomes and multiple X chromosomes.
• Men with Klinefelter syndrome usually have small testes, reduced facial and pubic hair and sterile
• Females with three X chromosomes have a tendency to be tall and thin (Poly X)
• Males with an extra Y chromosome usually are several inches taller than the average male
• At least one copy of an X chromosome is required for human development
• A female usually needs at least two copies of the X chromosome to be fertile.