Genetics Flashcards
Every living thing is organized via coded information called
Genetic material
Reproduction involves
Duplication and transmission of an organisms genetic material.
What is a gene?
A gene is an information entity. It is a sequence of DNA that codes for a single genetic instruction.
(Usually, this instruction is the sequence of a protein, but a gene may also serve to activate or deactivate other genes, in a cell or in neighboring cells.)
What is every aspect of our species based on?
- Information in genes
- Though the genes themselves do very little. It is the cytological machinery of our cells, passed from one generation to the next, that translate these instructions into living things.
The effects of every gene depend both on
other genes and the environment.
What is an allele?
ONE variation of a gene. Many genes have two, several or many different variants of the same basic genetic information.
What affect can alleles have on an organism?
Some are minor differences, while others can cause profound changes.
Nucleotide substitutions in the third codon position often produces no change at all. Why?
Because they code for the same transfer RNA and thus the same protein is produced.
Sickle cell anemia is caused by
A single nucleotoid substitution.
*GAG to GUG changes normal hemoglobin to hemoglobin that “sickles” under low oxygen concentrations.
Prokaryotes
Include the archaea and bacteria, are the simplest, oldest and most common organisms on the planet.
How does this typic genome of the prokaryote come to a typical eukaryote
The typical prokaryote has a much smaller genome
Stretched out, the DNA in E. coli would be (how large compared to the cell?)
500x longer than the cell itself.
What are the forms of gene exchange in prokaryotes
- NOT sexual reproduction
* swapping plasmids
gene
Indicate the hereditary determinant for a trait.
Alleles
Different versions of the same gene responsible fo rthe variation in the traits.
Genotype
The alleles found in a particular individual.
Histones
important and very evolutionarily conservative proteins. Loops of DNA are wrapped around one histone and locked in by a second, forming a structure called a nucleosome.
Mitosis
- The duplication of the genetic material within a eukaryote cell
- A duplication of the genetic complement of a eukaryote cell, Since it is usually followed by cell division, it can lead to growth, in a multicellular organism, or asexual reproduction, in a single-celled organism.
Does mitosis produce gametes
NO. In sezual organisms, mitosis is peripheral to sexual reproduction, it serves to give rise to the cell types which ultimately “kill themselves off” by splitting and splitting again into 4 very different cells
Sexual reproduction
A particular type of reproduction, a sharing of genetic material to form an individual with equal contributions from two separate parents.
THIS INVOLVES
*Formation of haploid sex cells, called gametes, from a diploid cell, a process called Meiosis
*Syngamy (or fertilization), a combination of genetic information from two separate cells to form a diploid cell, called a zygote.
In sexual reproduction where to the gametes come from?
Gametes usually, but not always, come from separate parents (egg and sperm)
in sexual reproduction both gametes are _______ and the resulting zygote is _______
haploid
diploid
Diploidy
The state of having two copies of every single gene
Some examples of organisms who are diploid
humans
flies
zebras
potatoes
Homozygous
Two copies of every gene are identical matches
Heterozygous
Subtle differences between the two copies of a gene
Meiosis
The process by which a single diploid cell gives rise to four, genetically different, haploid cells.
- The diploid progenitor duplicates its genetic material, each chromosome finds its match, four strands cluster in the structures. “crossing over”may occur. *Homologous chromosomes separate
- chromatids separate
Errors in meiosis
Have the potential to produce unusual phenotypes in the offspring
nondisjunction
most common meiotic error. An entire homologous pair of chromosomes migrates to the pole of a cell without splitting.
The human condition of Down’s syndrom results from
An error in meiosis.
A trisomoy at chromosome 21, or the sex chromosomes.
How do meiosis and sex produce variation?
meiosis-makes 4 cells with DIFFERENT sets of alleles, although the have the same GENES
Recombination
a result of crossing over, new combinations of alleles on chromosomes may arise.
This can produce variation.
Crossing over
a cytological phenomenon that occurs during the first of the two meiotic divisions.
- two strands of DNA form complimentary chromosomes cross over each other, and a break forms.
- Break is quickly repaired, switching stretches of DNA to create two new chromosomes.
- **Creates new combinations of alleles on chromosomes and permits favorable alleles to combine together on the same chromosome.
Genetic result of crossing over is called…
recombination
locus
means location, and it refers to the place where variation can occur.
segregation
the process by which a gamete comes to have only one of the two alleles it’s parent possesses, for every gene. It is random, and it occurs because of the separation of homologous chromosomes during the first meiotic division
assortment
Accounts for the fact that most eukaryotes possess many pairs of chromosomes, is is segregation at two or many loci simultaneously. Assortment is responsible for the variation in gametes created by the random selection of chromosome from each pair into gametes.
when genes are on separate chromosomes, it is said that they assort ________.
When they are on the same chromosome they tend to get passed on ______, which can only be broken by recombination, this is called________.
Independently
As a unit
Linkage
Morphological variation examples
hair color, height, eye color etc.
Behavioral variation
preference for foods, knowledge of languages, choice of clothing.
Variation within the white-cheeked rosella.Based on a diagram of where they are from call you tell if the variation is genetic, environmental or both.
4 varieties with its own distinct color combination and marking.
You can not tell based on a diagram of where they are from.
Attributes
But be scored, but do not fall into a continuum.
ex-eye color, political party, blood type, gender
Quantitative or measurable variables
fall along a measurable axis, and can be measured to observe their place relative to others.
Discontinuous measurable variables
Fall into discrete intervals. Example-shoe size, number of mates, number of arrests for drunk driving.
Continuous measurable variables
Do not fall into discrete intervals, exist along a continuum. Ex- height, weight, age
statistical population
The group of individuals in question.
histogram
the range of values for the category is broken into intervals, and the number of individuals withing that interval is expressed as the height of a bar.
Skewed distribution of histogram
more heavily on one side that the other
Normal distribution of a histogram
Looks like a bell curve
Standard deviation
the square root of variance
variance
the variability of values in the data set, their tendency to depart from the mean. sum of (x-mean)^1/N-1
Recessive alleles are only expressed in the
homozygous state
Alleles for albino coloration in many animals result from __________.
recessive alleles.
Codominance or incomplete dominance
the allelic interaction where, in heterozygous state, both alleles are expressed, or the heterozygote is in between the phenotypes of the homozygous individuals for those alleles.
in chickens black feather color is codominant with white feather color. What would heteroxygous chickens look like?
They would have black and white feathers in a checkered pattern.
How many loci does human blood type involve?
3, which exhibit both dominance and codominance.
I^A, I^b i^o
How many genes do bacteria have?
About 1,200 genes
How many protein coding genes do human beings have
20,000
How many protein coding genes do rice have?
about 38,000
What organisms have the largest genome?
Flowering plants, catfish, amphibians
No all loci have multiple alleles?
no, only a small percentage of loci have multiple alleles, perhaps 1-5% or less, depending on the species.
Genes interact with the environment to produce a _____________.
phenotype
Norm of reaction
describes the pattern of phenotypic expression of a particular genotype across different environments.
A chicken with black feathers is mated to a chicken with white feathers. 9 offspring in F1 all have checkered black and white feathers. 2 of the F1 mate a produce their own offspring. Diagram the cross, and predict the phenotypic composition of the next generation of F2
Start by listing the genotypes of the P1s, this is part of the answer, and you will get nowhere if you skip right to a Punnet square.
The P1s are FwFw and Fb Fb
The white parent can produce one type of gamete, Fw, the black parent can produce one type of gamete, Fb. Note, gametes are always haploid.
The F1 are all FwFb, this is the only possible genotype, given the two parents. Note, adults are always diploid.
These F1 can produce two types of gametes, Fw and Fb.
To produce an F2, these two gametes can unite in four possible ways.
The male F1 parent can produce a Fw or a Fb
The female F1 parent can produce a Fw or a Fb
This gives:
Fw from the male parent x Fw from the female-white chicken
Fb from the male parent x Fb from the female-black chicken
Fw from the male parent x Fb from the female-checkered
Fb from the male parent and Fw from the female-checkered
The colors in the offspring are ¼ black, ¼ white, ½ checkered.
If you answered ¼ to ¾, you should consider that this is a codominant system.
law of independent assortment
the “particles” for each gene segregate independently of each other (from mendel)
law of segregation
these “particles segregate, so that individuals with two particles produce gametes with only one particle. (from mendel)
how do we get degrees of freedom for a chi square cross?
N-1
Linkage
the result of two loci being located close together on the same chromosome. It causes a departure from independent assortment.
How can you tell how far apart loci are?
*The proportion of the F2 from a test cross that are recombinants.
Take the number of recombinants and divide by the total, and that gives you r-the proportion of recombinants.
(HINT-recombinants are the F2 that do not resemble the grandparents)
*From r multiply by 100 and you have the distance in map units.
Loci that are very close together are said to be….
tightly linked, produce few recombinants.
