Chapter 2 Flashcards
Sperm
Male reproductive cell
Ovum
Female reproductive cell
Gametes
Male and female reproductive cells.
Huge amount genetic info
Zygote
Fusion of sperm and ovum. Hour after sperm enters ovum
Genes
Basic units of genetic info
How many human genes
25,000
DNA molecules
Code for all cells in body. Substance genes are made of
Chromosomes
Rod shaped bits of DNA organized in 23 pairs. (46 chromosomes)
Chromosomes in sex cells
23
Mitosis
One cell makes 2 identical.
Most cells reproduce this way
Chromosomes in zygote
46
Meiosis
Cell division where cells have half number of chromosomes. Gametes (sex cells)
Genetic duplicate/ monozygotic twins
Identical twin
Less than ___ % of all pregnancies produce twins
3
T/f: multiple births are less likely to occur for triplets or higher order multiples
True
Why do multiple births occur?
Bit of cells breaks off (monozygotic)
2 eggs are fertilized by different sperm at close time (Dizygotic)
What increases chances of multiple births?
Age
Use of fertility drugs
Some parts of _____ _____ have the highest rate of Dizygotic births in the world
Central africa
T/f having multiple children carries same risk?
No, risk increases with number of babies
Which pair determines sex of child?
23rd
Dominant trait
Trait expressed
Recessive trait
Present but not expressed
Genotype
Combination of genetic material present but not visible
Phenotype
Genetic info contained and seen
