9.1-9.10: Mendel's Laws Flashcards
(70 cards)
Give a brief history on the study of genetics:
- Hippocrates: suggests that pagenes from parent organisms create a child, however pagenes are subject to change as the human body develops.
- The blending theory: 19th century biologists suggested that human traits were a blend of their parents
End of 9.1 Question: Imagine you have two different houseplants of the same species, one of which blooms with white flowers and the other with red flowers. Design a simple experiment to test the blending hypothesis
Cross the two plants and observe the resulting flower color in the offspring. The blending hypothesis predicts the appearance of pink flowers.
Define heredity
the transmission of traits from one generation to the next
Define genetics
The study of heredity
What was the outcome of Mendel’s pea experiment? What did he conclude?
That genes were discrete: no blending, just shuffling.
Define character, in the field of genetics?
A heritable feature that varies among individuals (ex. eye color)
Define trait, in field of genetics
each variant for a character (ex. blue eyes, brown eyes)
Why were peas such a good selection for Mendel’s experiment?
Because they self-pollinated, and if Mendel put bags on top of them, there was not cross pollination that happened. However, he could also use the isolatedness of the reproductive anatomy to his advantage; he could cut it off and dust it with pollen, then plant the developed seeds. The genes for all his traits were on separate chromosomes. The traits were binary choices.
Define true-breeding varieties, in the field of genetics
varieties for which self-fertilization produced offspring all identical to the parent.
Define hybrids, in the field of genetics
The cross of two different (true-breeding) varieties of plants
what is a short term for cross-breeding?
cross
What are the generations of the the true-breeding cross called?
P(arental) generation
F1(ilial) generation.
When F1 plants self-fertilize, they are called F2. (remember, these are plants that Mendel experimented on)
End of 9.2 Question: Describe three generations of your own family using the terminology of the genetic cross.
The P generation are your grandparents, the F1 your parents, the F2 is you (and siblings)
Define monohybrid cross.
A cross between plants observing only one character (Mendel crossed a true-bred white flower and purple flower).
When Mendel crossed the true bred white flower and purple flower, what were the F1 generations results? The F2? What did he deduce from these results?
F1, all flowers were purple.
F2, 3/4 flowers were purple 1/4 was white.
The heritable factor for the white flowers did not disappear in the F1 generation, but was masked by the purple flower. The F1 plants must carry two factors for flower-color character, one for purple and one for white.
What are alleles?
Alternative version of a gene (a SINGLE gene in a SINGLE chromosome. There may be mistakes with wording later in the cards)
Mendel’s first hypothesis is: There are alternative versions of genes that account for variations in inherited characteristics. Put this in the context of his experiment.
The F1 plants must carry two factors for flower-color character, one for purple and one for white, despite all being purple, because the F2 generation had white flowers.
Mendel’s second hypothesis is: For each character, an organism inherits two alleles, one from each parent. Put this in the context of his experiment.
Allele for white flowers, allele for purple flowers.
Define homozygous
An organism that has two identical alleles for a gene. The trait itself is a homozygote.
Define heterozygote:
An organism that has two different alleles for a gene, called a heterozygote.
Mendel’s third hypothesis is: If the two alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele; the other has no noticible effect on the organism’s appearance and is called the recessive allele. Put this in the context of his experiment.
Heterozygous plants always appeared purple, making purple the dominant allele.
Mendel’s fourth hypothesis is: A sperm or an egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes (Law of Segregation). Put this in the context of his experiment.
Genes determining flower color come together when an egg is fertilized. They can be PP, Pp/pP, or pp, determining color.
How are recessive and dominant traits represented by scientists?
lowercase and uppercase letters, respectively.
Why did the F2 generation have 25% of its offspring with white flowers.
Because of the law of segregation and recessive and dominant traits. The P generation had gametes of P&P and p&p. They all combined to form alleles of Pp. When the F1 generation (Pp) self-fertilized, there were four gametes: P&p and P&p. Then, instead of one outcome there were three: PP, Pp and pp. (Pp also pP). The each account for 1/4. But, P is the dominant trait, meaning 3/4: PP, Pp, and pP, would all be purple, and only 1/4 would be white.
