Meiosis and the Scientific Method Flashcards
Explain the cycle of scientific enterprise.
theory, hypothesis, experimental tests, new facts, “are the facts consistent with the theory?” NO: “can theory be altered to accommodate new facts?” (NO: new theory with facts. YES: altered theory with facts.) YES: theory with more facts, new hypothesis
the cycle of scientific enterprise
the model of how we make and test theories
theories
mental models for how the natural world looks
hypothesis
specific answer to a specific question, if…then statement, testable
fact/data
supported by observable evidence
scientific method
a logical method or procedure to follow when doing the experiment
controls, control group
not exposed to testing
experimental group
one you are experimenting on (changing something)
independent variable
the one thing you change between the 2 groups
dependent variable
the change/ the thing that will determine the result, what you are measuring
the purpose of mitosis
growth, repair, and replacement
heredity
the passing of traits from one generation to the next
genetics
the study of herdity
asexual repro.
a single parent passes on its genes to its offspring
sexual repro.
humans do this, 2 parents giving genes to their offspring creating a unique set of genes
what do chromosomes contain and what is their purpose?
contain: DNA and genes
purpose: protection and organization while dividing
genes
recipe for making proteins, segment of DNA that codes for a particular protein, gives us our individual looks
karyotype
a picture of all of your chromosomes in a cell, arranged in pairs from large to small
homologous chromosomes
same types of genes for the same traits, 2 sister chromatids
sex chromosomes
1 pair of chromosomes, determine gender: x and y = boy; x and x = girl
autosomes
the other 22 pairs of chromosomes
Who determines the gender of the baby? The male or female?
male: 1/2 sperm = X and 1/2 sperm = Y, depends on which sperm fertilizes the egg
haploid/diploid
n = haploid. 2n = diploid. [n = {23 chromosomes}]
sex cells
haploid, come from germ cells (what makes the egg and sperm)
gametes
the reproductive/sex cells
zygote
a fertilized egg, diploid cell, from mom and dad
meiosis
division of germ cells to make sex cells
alternation of generations
a life cycle that alternates between haploid and diploid cells
explain the circle of life
zygote, mitosis, adult, meiosis, fertilization, back to zygote
Explain Meiosis
- Interphase: DNA coils
- Meiosis 1:
- Prophase: chromosomes form and create homologous pairs which form tetrads, synapsis occurs: pairs stick together, swap DNA: homologous chromosomes take a bit of each others’ DNA at chiasmata to form recombinant chromosomes, why no 2 humans are the same, nucleic membrane dissolves
- Metaphase: pairs move toward metaphase plate
- Anaphase: pairs separate into sister chromatids
- Telophase/Cytokinesis: cells pinch off, DNA does not uncoil
- Meiosis 2:
- prophase: chromosomes already formed, spindle forms again
- metaphase: chromosomes positioned at metaphase plate
- anaphase: sister chromatids separate
- telophase/cytokinesis: cells pinch off to form 4 haploid cells
overview of meiosis
start with 46 chromosomes. meiosis 1: 23 pairs left. meiosis 2: 23 chromosomes left.
chiasma
the point at which homologous chromosomes attach exchange DNA
recombinant chromosomes
chromosomes with exchanged DNA
another name for meiosis 1 and 2
meiosis 1 = reductional phase
meiosis 2 = equational phase
three sources of genetic variation
- crossing over- recombinant chromosomes (prophase 1)
- independent assortment- how maternal and paternal chromosomes line up/are arranged
- random fertilization- any sperm and egg could fertilize each other
who is Gregor Mendel?
1800’s, father of modern genetics, Austrian monk
Where are the reproductive organs in plants?
the flower
what plant did Mendel use in his experiments?
pea plants
How could Mendel control the breeding of the pea plants?
If he didn’t want 2 plants to fertilize each other, he could cut off the male gametes (things that made pollen) on the flower. If he did want 2 certain plants to fertilize each other, he would take a brush to collect the pollen from one plant and use it to pollenate another one.
true breeding
a white flower + a white flower = a white flower
what are the 3 generations in plants?
P generation- parental generation
F (1) generation- the first filial generation
F (2) generation- the 2nd filial generation (f1 xf1)
locus
where genes are located on a chromosome
allele
alternate forms of a gene found at the same locus on homologous chromosomes (gene for color)
Mendel’s 4 Important Findings
- There are “factors” in living things that are inherited by offspring.
- These “factors” occur in pairs. Today we know these “factors” are genes. The alternate versions of a gene are called alleles.
- Dominant factors are always expressed. Recessive ones have no effect.
- the law of segregation- the 2 factors for a trait separate during gamete formation (anaphase).
How do you represent dominant and recessive traits?
P- purple T- tall dominant traits = capital letters, recessive = lowercase, keep same letters p- white t- short
homozygous
2 of same genes in zygote
heterozygous
2 different genes in zygote (dominant wins)
phenotype
physical appearance
genotype
genetic makeup
punnet square
developed by Reginald Punnett, a tool to determine the allele composition of offspring from a cross between 2 individuals
