Chapter 5 Flashcards
Sexual Reproduction
- formation of offspring that are genetically distinct from parent
Sex is defined by:
- phenotype of the individual
Sex Determination Mechanisms
- Chromosomal Sex Determination
- Genetic Sex Determining
- Environmental Sex Determining
Chromosome theory of inheritance
- genes are located on chromosomes and chromosomes are substrate for gene segregation
_____ said male insects had a strange body in the nuclei= X body
- hunking
_____ said male grasshoppers have a heterochromosome and female grasshopper cells had one more chromosome than males
- McClung
_______ said female mealworms have 20 large chromosomes and males have 19 large and one smaller (Y)
- Stevens
____ said female butterflies have two X chromosomes and males have one X
- WIlson
All mammals chromosomes are:
- XX/XY
In simple systems what is the chromosomal sex determination
- XX for females
- XO for males
O=no chromosome
At _____ half sperm receive X and other half gets no chromosome
- meiosis
Heterogametic sex
- sex that produces two different gametes
Homogametic sex
- sex that produces identical gametes
What is a ZZ/ZW chromosome sex determination?
- male is homogametic (ZZ)
- female is heterogametic (ZW_
- female produces two diff gametes, half with Z other half with W
In haplodiploidy what is the result?
- males are haploid (1n) bc develop from unfertilized eggs
- females are diploid (2n)
- sex is determined by the number of chromosome sets
Are there any sex chromosomes in genetic sex determination?
- no, there is no obvious difference
In genetic sex determination what determines the sex of the individual?
- genes
In environmental sex determination what is it dependent on? Give example
- temperature dependent
- alligators in warm temperatures during embryonic development produces males and in cool weather will produce females
Nondisjunction
- When the X chromosome fails to separate in Anaphase 1 of meiosis
- some eggs get two copies of XX and others get more
Sex determination in Drosophilia
- Females XX, males XY, but Y does not determine maleness
- the ratio of autosomes to X determine the sex = genic balance system
- X has female producing genes, and autosomes have male producing genes
In drosophilia what is sex determined by?
- the X:A ratio (# of X chromosomes/ # of haploid sets of autosomes)
Turner Syndrome
- females don’t undergo puberty, immature secondary female characteristics
- low hairline and folds of skin on neck
- may have cognitive impairment or sterility
- XO
- also known as 45, X
Klinefelter Syndrome
- males
- small testes, breast enlargement, reduced facial/pubic hair
- one or more Y chromosome, multiple X chromosomes
- often sterile, may have mild cognitive impairment
- also known as 47, XXY
Poly-X Females
- Triplo-X syndrome (XXX)
- tall, thin, sometimes normal fertility, normal intelligence
- XXXX, XXXXX has normal female anatomy, but cognitive impairment
- severity increases in # of X chromosomes