genetics 1a

T/F The central dogma is only found in humans

false, it occurs in many species

T/F Most mutations are neutral

true

T/F DNA replication is semiconservative (one new and one old strand)

true

How do mutations affect germline cells?

it creates heritable variation

How do mutations affect somatic cells?

it can shorten lifespan

What does deleterious mean?

a mutation that causes harmful results

Why are Mendel's laws not always applicable?

it only is accurate for simple traits, not complex traits such as eye color or skin color

What is genetics?

the study of heredity and variation, how organisms have certain traits

What is the order of the central dogma?

DNA -\> RNA -\> Protein

T/F Genes are only expressed at the molecular level

false, they are expressed at the molecular, cellular, organism, and population level

What is a homologous pair?

pair of chromosomes, one from each parent

How many chromosomes do humans have?

46 (23 pairs)

What is an autosome?

non-sex chromosome (22 pairs)

How long is the human genome?

3.2 billion bases long (25,000 loci)

What features of DNA do we share with all life?

basically everything (have DNA, double stranded, semiconservative, etc)

What are alleles?

different versions of the same gene on homologous chromosomes

What is a mutation?

change in DNA sequence

T/F Both somatic and germline mutations are transmitted over generation

false, only germline mutations are

T/F Mutations can only occur in the coding section of DNA

false, they can occur in the coding and noncoding sections

What is a single nucleotide polymorphism (SNP)?

a single base substitution between individuals (aka silent mutation)

What is a cis regulatory switch (CRE)?

is in noncoding section of DNA, determines when where and quantity instructions for transcription and protein

What is a trans DNA sequence?

part of DNA that goes through the central dogma

What level does mutation occur at?

DNA level

What does it mean when mutations are described as being "stocastic"

they are randomly distributed through the genome

What are autosomal recessive inheritance patterns associated with?

loss of function mutations

What is loss of gene function (LOF)?

mutation causes protein to be nonfunctional

What happens if a CRE is turned off/broken?

loss of function

What does it mean if you are a heterozygote for a autosomal recessive mutation?

you are a carrier

What are autosomal dominant inheritance patterns associated with?

gain of function mutations

What is a gain of function mutation (GOF)?

a mutation where too much protein is produced or it isn't doing what it is supposed to

For autosomal dominant heterozygotes, what does H in Hh represent?

H\= gain of function allele
h\= normal allele (NOT a carrier, does have the disease)

In autosomal dominant GOF mutations, explain the difference of the protein if it occurred in the cis vs trans section of DNA?

cis\= protein is normal, excessive quantity produced

trans\= protein produced with an an incorrect amino acid/doesn't function correctly

What is a missense/nonsynonymous/replacement mutation?

point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid

What does synonymous mean?

one base codes for the same protein as another base (ex. GAA and GAG both code for Glu)

What is a nonsense mutation?

a mutation where a stop codon is formed early, forms a truncated protein (short protein)

What is a frameshift mutation?

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide that isn't in a set of 3

Which mutations are LOF and which are GOF?

SNP\= none
missense\= GOF or LOF
nonsense\= LOF
frameshift\= LOF

What is an example of a missense mutation disorder?

sickle cell anemia

What is an example of a nonsense mutation disorder?

cystic fibrosis

What is an example of a frameshift mutation disorder?

tay-sachs

What is the effect of a mutation on the promoter sequence?

may increase or decrease the rate of transcription

What is the effect of a mutation on the regulatory element/operator site?

may disrupt the ability of the gene to be properly regulated

What is the effect of a mutation on the 5'-UTR/3'-UTR?

may alter the ability of the mRNA to be translated, may alter the mRNA stability

What is the effect of a mutation on the splice recognition sequence?

may alter the ability of pre-mRNA to be properly sliced

How is cystic fibrosis inherited?

recessive, both parents have to pass on LOF not just one, causes LOF in CFTR protein

What three mutations cause a LOF allele?

missense, frameshift, nonsense

How many alleles are needed to have a LOF phenotype?

2, one from each parent must be LOF

What kinds of mutations cause a GOF allele?

duplication, missense

Is GOF autosomal dominant or recessive?

dominant, it only takes one allele to increase protein toxicity

If a mutation in CRE causes inappropriate protein function is it GOF or LOF?

GOF, can cause protein to be in incorrect location, quantity, and timeframe

If a mutation in CRE causes no protein function is it GOF or LOF?

LOF, no protein is produced

How many SNPs are in the human genome?

3 million

How does a frameshift mutation affect the open reading frame (ORF)?

it causes the reading frame to be shifted (addition/deletion)

What is a nucleotide?

Nitrogen base + sugar (ribose or deoxyribose) and phosphate group (ACGT)

What is gene expression?

the process by which DNA directs protein synthesis

What is a genetic disease that is caused by genes and the environment?

PKU- can be controlled by eating foods without phenylalanine

What is a point mutation?

a mutation changing a single base pair within the DNA (type of base substitution)

What is a base substitution?

a mutation where one base is substituted for another

T/F Transcription can only in euchromatin and heterochromatin.

false, transcription only occurs in euchromatin

What is DNA packed into?

chromosomes

What are histones?

proteins that DNA wraps around

What is mitosis?

an ongoing process that produces two daughter cells that are genetically identical to the parent cell

Where does mitosis occur?

in somatic cells

T/F Mitosis can only have diploid cells?

False, in humans they are diploid cells but in other organisms they can be haploid, diploid, or polyploid

Explain what causes aging.

mitosis becomes slower and less accurate over time

What happens in synthesis of the cell cycle?

replication of DNA occurs and the cell divides

What are sister chromatids?

caused by duplication of chromosomes at S phase, contain identical DNA sequences

What are homologous chromosomes?

result from obtaining a set of chromosomes from both parents, contain same genes but may differ slightly in sequence

What is the order of mitosis?

PMAT:
Prophase
Metaphase
Anaphase
Telophase (cytokinesis)

What happens in prophase/prometaphase?

centrioles and spindle fibers appear, chromosomes condense so sister chromatids can be joined at centromere, nuclear membrane breaks down (23 pairs of chromosomes in cell)

What happens in metaphase?

sister chromatids line up at metaphase/equatorial plate, NO pairing of homologous chromosomes

What happens in anaphase?

centromeres are pulled apart by spindle fibers, each chromatid from sister is pulled to opposite pulls, still 23 pairs on each side

What happens in telophase?

chromatids expand back to chromosomes, nuclear membrane reappears, cytokinesis begins (23 pairs per cell)

How many genomes are in the nucleus of each cell?

1

T/F DNA is copied during mitosis/meiosis

false, it happens in the nucleus before both

What does degenerate mean?

multiple codons can code for the same amino acids

How often do SNPs occur?

every 1 in 1000 base pairs

How many alleles does each genomic loci have?

2, one from each parent

What does polygenic mean?

many genes influence one phenotypic trait

Is most of the genome coding DNA (genes) or non-coding DNA?

noncoding

What are suppressor/compensatory mutations?

reverse or greatly alleviate the phenotypic consequences of the initial mutation (ex. autism is on a spectrum)

What is interphase?

G1, S, G2

What is meiosis?

starts with zygote, produces four haploid cells that are genetically different from the parent cell

T/F In females all 4 gametes become eggs

false, only 1 becomes an egg, the other 3 turn into heterochromatic and are unused

What does meiosis produce?

germ cells oocyte (limited) and sperm (unlimited)

What happens in prophase I of meiosis?

homologous chromosomes pair, form tetrads, crossing over occurs

What is a tetrad?

4 chromatids paired together

What happens in metaphase I?

tetrads line up at metaphase plate, pairs are NOT attaches at centromeres

What happens in anaphase I?

each homologous pair migrates to opposite poles

What is recombinant?

a sister chromatid that has DNA from both parents after crossing over

What happens in telophase I?

two cells form with 2n chromosomes, however they are not identical genomes

What happens in prophase II?

no crossing over occurs, spindle fibers form

What happens in metaphase II?

sister chromatids line up at the metaphase plate

What happens in anaphase II?

sister chromatids are separated with each chromatid pulled to opposite poles

What happens in telophase II?

results with 4 haploid cells, known as reduction division, each cell has unique genome

What is the difference between aneuploidy and nondisjuction?

aneuploidy- name describing an abnormal karyotype, variations in chromosome number

nondisjunction- the process where chromosomes fail to seperate, causes aneuploidy

Where do most aneuploidy errors occur?

meiosis, however rarely they can occur in mitosis

What is the result of nondisjunction in anaphase I vs anaphase II?

anaphase 1\= creates 4 abnormal cells

anaphase 2\= creates 2 normal and 2 abnormal cells

What does 47,XXY signify?

47 chromosomes, 2X 1Y, klienfelter syndrome

What does 47, XYY signify?

47 chromosomes, 1X 2Y, jacobs syndrome