Chapter 7- genetics Flashcards
What is genetics?
The scientific study of heredity
What is heredity?
The passing on of characteristics from parents to offspring (these characteristics are called traits)
What traits did Mendel study?
Height, seed color, and flower color
What type of plant did Mendel use to study heredity?
True breeding pea plants
What does the pistil produce?
Female sex cells (or eggs)
What does the stamen produce?
Pollen which contains male sex cells (or sperm)
When does a new organism begin to form?
When egg and sperm cells join in the process of fertilization
What needs to happen in order for fertilization to occur?
Pollen must reach the pistil of a pea flower (this is called pollination)
What is self pollination?
Pollen from a flower lands on the pistil of the same flower
If a true breeding plant has purple flowers then what will it produce?
It will only produce plants with purple flowers
If a true breeding plant (purple) was allowed to self pollinate then what would happen?
They would only produce offspring identical to themselves
How many traits of pea plants did Mendel study?
7
How many traits at a time did Mendel study?
1
How did Mendel see how height was passed from parent to offspring?
He took pollen from a true breeding tall pea plant and cross pollinated a true breeding short pea plant?
What did Mendel notice after seeing how heights was passed from parent to offspring?
He noticed that a trait from the parent pea plant did not always show up in the offspring (1st generation)
What method did Mendel use to better control his experiments?
Cross pollination
What part of the flower contains pollen?
Anthers
Why did Mendel remove the anthers in his experiments?
So that the flower could not self pollinate
What happened when Mendel crossed true breeding (purple-flowered) plants with true breeding (white-flowered) plants?
The 1st generation produced all purple flowered plants (homozygous dominant and recessive cross)
What happened when the purple flowered plants of the offspring self pollinated ?
White flowers reappeared (heterozygous cross)
Hybrid
Offspring of parents that have different forms of a trait
What did Mendel conclude?
- sets of genetic info. must control the inheritance of traits in peas
- the factors that control each trait exists in pairs
- the female and male parent both contribute one factor
- one factor in a pair can mask, or hide, the other factor
What are the factors that determine traits called?
Genes
Alleles
Different forms of genes
What are an organisms’ traits controlled by?
The alleles it inherits from its parents
What are the two options for an allele?
Dominant, recessive
Dominant allele
An allele whose trait always shows when the allele is present
Recessive allele
Hidden whenever the dominant allele is present (can only show with two recessive alleles)
What do geneticists use to represent alleles?
Letters (dominant= capital, recessive= lowercase)
Law of segregation
- every organism has two alleles of each gene
- when gametes are produced the alleles separate
Phenotype
The way an organism looks and behaves (you can physically see it)
Genotype
The allele combination of an organism
Law of Independent Asoortment
-genes for different traits are inherited independently of each other
Probability
A number that describes how likely something is to happen
What law describes what is likely to occur (not what will occur)?
Law of probability
Punnett square
Chart that shows all the possible ways an allele can combine in a genetic cross
What is the combination of alleles that parents can pass on to an offspring based on?
Probability
Monohybrid
Cross of one trait
How many chromosome do sex cells have?
Half as many chromosomes as the body cells have
Diploid
A complete set of chromosomes
Haploid
A half set of chromosomes
Meiosis
Process by which the number of chromosomes is reduced by half as sex cells form
Result of meiosis
4 genetically different haploid cells
Where does meiosis occur in?
A diploid cell
How many cell divisions does meiosis go through?
2
How many interphases are there in meiosis?
1
Interphase
Chromosomes double and thicken
Prophase 1
Nuclear membrane disappears (spindle fibers attach)
Metaphase 1
Homologous pairs line up in the middle
Anaphase 1
Homologous pairs separate (not the chromosomes)
Telophase 1/ cytokinesis 1
- nuclear membrane reforms
- cell splits
Prophase 2
Nuclear membrane disappears (spindle fibers attach)
Metaphase 2
Chromosomes line up at center
Anaphase 2
Chromosomes split
Telophase 2/ cytokinesis 2
- nuclear membrane reforms
- cells split
Why are the 4 cells genetically different?
Cross-over and recombination
What happens in crossover?
Homologous chromosomes pair up (tangle)
What happens in recombination?
Parts of the chromosomes switch (trading sections of DNA)
