Heredity and Punnet Squares Flashcards
Genetics
The study of heredity and hereditary variation
Heredity
-The transmission of traits from one generation to the next
-Traits passed from parent to offspring through genes
Genes
-Segments of DNA that code for the basic units of heredity
-Offspring acquire genes from parents from inheriting chromosomes
Asexual reproduction
-Single individual
-No fusion of gametes
-Clones- offspring are exact copies of parents
-Mutations are the only source of variation
-Can reproduce asexually through mitosis
Sexual
-Two parents
-Offspring are unique combinations of genes from parents
-Genetically varied from parents and siblings
Homologous Chromosomes
A pair of chromosomes that are the same length, size and centromere position that carry the same genetic information
Karyotypes
A display of chromosome pairs ordered by size and length
Somatic cells
-Diploid or 2n: two complete sets of each chromosome
-Humans 2n: 46
Gametic cells
-Haploid or n: one set of chromosomes
-Humans: 23
What have DNA packaged in chromosomes?
Eukaryotes
Two types of chromosomes
- Autosomes: Chromosomes that don’t determine sex
- Sex chromosomes: X & Y
Life cycle
-Sequence of changes in the reproductive history of an organism from conception to its own reproduction
-Fertilization and meiosis alternate in sexual life cycles
Fertilization
When a sperm cell fuses with an egg to form a zygote
Meiosis
Process that creates haploid gamete cells in sexually reproducing gamete organisms
Three unique events in meiosis
- Prophase 1
- Metaphase 1
- Anaphase 1
Prophase 1
Synapsis: Homologous chromosomes pair up and physically connect to each other form a tetrad
-Crossing over (recombination) occurs at the chiasmata and DNA is exchanged between the homologous pairs
-Every chromatid that’s produced has a unique combination of DNA
Metaphase 1
Independent orientation-tetrads line up at the metaphase plate
Prophase II
-No crossing over
-Spindle forms
-Sister chromatids not identical
Telophase 1 and cytokinesis
-Nuclei and cytoplasm divide
-There is now a haploid set of chromosomes in each daughter cell
Anaphase 1
Pairs of homologous chromosomes separate
-sister chromatids still attached
Metaphase II
-Chromosomes line up at the middle
-Because of crossing over, chromatids are unique
Anaphase II
Sister chromatids separate
Telophase II and cytokinesis
-4 haploid cells
-Nuclei reappear
-Each daughter cell genetically unique
True breeding
Organisms that produce offspring of the same variety over multiple generations
