Heredity Lab Flashcards
Heredity
The passing on of physical characteristics from parents to their off spring
How are traits passed on?
Through chromosomes in sperm and egg cells
Chromosomes
DNA strands composed of gene units
Genes
Chromosome sections
• contains codes for specific physical and chemical characteristics
Define traits
Specific physical or chemical characteristics of an individual
•passed on with chromosomes in egg and Sperm cells
Type of traits
Dominant
Recessive
Dominant traits
Always seen expressed in offspring •free earlobe •hair in hands •bent fingers •tongue rolling
Recessive traits
Not always seen
•hidden traits
•not expressed
Inheritance traits
Many traits are inherited on pairs of genes located on separate homologous (look alike) chromosomes
Traits inherited on pairs of genes located on separate homologous chromosomes are called
Alleles genes
Phenotype
Physical appearance of an individual
Geneotype
Inherited gene combination for a specific trait
Two types:
•homozygous
•heterozygous
Homozygous
Alleles of pair have same information
DD dd
Heterozygous
Allele genes have different information
Dd
What is unique about the phenotype for the human trait, red hair?
Develops from a dominant allele on a different gene pair
•inhibits the expression of the first pair
Somatic cells
Make up the body structure
•most of cells that make up body structure are somatic
•contain 46 chromosomes 23 pairs
Name two reproductive cells
Sperm and egg
How many chromosomes do the reproductive cells contain?
Contain 23 chromosomes, one of each original pairs
Haploid
Another way to write chromosome numbers
•N=23 (only half)
Diploid
•2N=46
Meiotic division
- two cell divisions occur here
* go through 4 phases
Four phases of meiosis
Prophase
Metaphase
Anaphase
Telophase
What is the final result if meiosis?
4 daughter cells containing 23 chromosomes each
•male: 4 sperm
•female: 3 polar bodies
1 egg
Spermatogenesis
Process of sperm cell formation in the seminiferous tubules of the testes
Meiosis I
Primary spermatocytes divide to form two secondary spermatocytes
•cell duplicates chromosomes 46 to 92
•chromosome pairs separate In reduction division
•makes 46 and 46
Meiosis II
- secondary spermatocytes divide into spermatids
* chromatids separate into four 23 chromosome spermatids
Oogenesis
Process of egg cells formed in the ovary and released at ovulation
Stages if oogenesis
- oogonia cells are present from birth, only a few will develop into primary oocytes
- meiosis I and II
Meiosis I female
- first cell division prior to ovulation
- a secondary oocyte and polar body are produced
- chromosome pairs separate in this division
- 46 to 2x23 chromosomes
Meiosis II female
- occurs after ovulation
- single egg cell results, secondary oocyte
- equals 23 chromosomes and polar body with Xtra chromosomes
Karyotyping
- method of observing human chromosomes
- a picture of chromosomes is produced
- homologous pairs are arranged together
Chromosome types
- Autosomes
* sex chromosomes
Autosomes
Chromosome pair 1-22
•have genetic codes for most body parts
Sex chromosomes
23rd pair
•contain codes for sex of an individual
Female: XX
Male: Xy
Use if karyotypes
•determine sex of an individual
•determine chromosome number
•predicts phenotypes from normal or abnormal patterns
-may see missing chromosomes
-additions or deletions may be present on same chromosomes
Non-disjunction
Unequal separation of chromosomes during either meiosis I or meiosis II
Autosomal non-disjunction
Unequal separation of Autosomes chromosomes (1-22) during meiosis results in too few or two many chromosomes in sperm or egg cell
Sex chromosome non-disjunction
An unequal separation of the X or Y chromosomes occurs during meiosis I or II
Turners syndrome
45 total (only one X chromosome) •phenotype: female
Fertilization
- union if sperm (23) and egg (23)
- the resulting fertilized cell called zygote
- has 46 chromosomes total
Identical twins
- cells become separated early in cleavage process, each cell forming new individual
- each has same genetic make up
- look alike
- monozygotic formation
- 1 egg
Monozygotic formation
Coming from a single zygote
Fraternal twins
More than one egg, fertilized by separate sperm cell •dizygotic •different genetic make up •same or opposite sex •multiple eggs
Dizygotic
2 different zygotes are formed