Chapter 13: Textbook Flashcards
Cystic fibrosis is an autosomal
Recessive disorder
Heredity
Transmission of traits from one generation to the next
Hereditary units
Genes
Define gene locus
A gene’s specific location along the length of a chromosome
Define asexual reproduction
A single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes
Define clone
An individual that reproduces asexually gives rise to a clone
Define sexual reproduction
2 parents give rise to offspring that have unique combinations of genes inherited from the two parents
Define life cycle
Generation to generation sequence of stages in the reproductive history of an organism from conception to reproduction
Ordered display of chromosomes from longest to shortest
Karyotype
Homologous chromosomes
The two chromosomes of a pair have the same length, centromere position and staining pattern
Any cell with two chromosomes is called
A diploid cell
For humans the diploid number is
46
2n = 46
n = 23
Gametes are
Haploid cells (23 chromosomes)
Define fertilization
Union of gametes culminating in fusion of their nuclei
Zygote
Resulting fertilized egg
Gamete formation involves
Meiosis
What happens as a result of meiosis
Human sperm and egg is haploid, fertilization restores the diploid condition by combining two haploid sets together
Define the steps of Meiosis I
Prophase I
- nuclear envelope breaks down
- chromosomes condense
- crossing over occurs: DNA molecules of non sister chromatids are broken and are rejoined to each other
Metaphase I
- pairs of homologous chromosomes are now arranged at the metaphase plate
Anaphase I
- breakdown of proteins the hold sister chromatids together
- move towards opposite poles
Telophase I and cytokinesis
- each half of the cell has a complete haploid set
- cytokinesis forms two haploid daughter cells
Meiosis I creates
2 haploid daughter cells
Describe meiosis II
Prophase II
- A spindle apparatus forms
Metaphase II
- The chromosomes are positioned at the metaphase plate as in mitosis
- Because of crossing over, the two sister chromatids of each chromosome are not genetically identical
Anaphase II
- breakdown of proteins holding sister chromatids. Chromatids move toward opposite poles
Telophase II and cytokinesis
Chromosomes begin de condensing
- produces four daughter cells each with a haploid set of chromosomes
Crossing over
When one or both of chromatids include regions of the non sister chromatid DNA
Describe the process of crossing over
Each gene on one homologue is aligned with the responding gene on the other homologue. The DNA of two nonsister chromatids are broken down by specific proteins. Synaptonemal complex holds one homologue tightly to the other. This association is called the synapsis and during it the DNA breaks are closed up so that each broken end is joint to the corresponding segment to join paternal to maternal chromatid
Three unique events to meiosis
- Synapsis and crossing over
- Alignment of homologue pairs at the metaphase plate
- Separation of homologues
Differences in roles of mitosis and meiosis
Mitosis: enables multicellular animal or plant to arise from a single cell
Meiosis: produces gametes
Define independence assortment
The alleles of two or more different genes get sorted into gametes independently of one another
Define recombinant chromosomes
Individual chromosomes that carry genes derived from two different parents
