all traits of parents are blended in their offspring. males and females produce a liquid for reproduction and so it was reasoned that the liquids would blend to form an intermediate mixture in the offspring
what are 2 problems with the blending inheritance model?
a. all individuals will eventually look alike
b. some traits skip a generation and appear in the next, unblended
austrian monk, published results in 1865, trained as a physist so had a quantitative background. began breeding peas to study patterns of inheritance. father of modern genetics
particulate model of inheritance
mendel's idea. parents pass discrete particles (Alleles) to their offspring that do not physically blend with other particles
2 copies of every chromosome/gene
a pair of the same chromosomes, one copy from each parent
one copy of every chromosome, half the number you need
name for haploid eggs and sperm
why are gametes haploid
if they were not, chromosome number would double each generation
piece of DNA that codes for a protein
different forms of the same gene
physical description of an organism's traits ex: tall, short
describes which alleles are present ex: AA, AB
homozygous allele pairing
2 copies of same allele, can be dominant or recessive
heterozygous allele pairing
2 different alleles
one allele hides the appearance (phenotype) of another
name for hidden allele
phenotype of heterozygote is intermediate between phenotype of 2 homozygous genotypes (red and white make pink flowers)
phenoptye of heterozygote simultaneously shows both phenotypes (blood type)
2 or more alleles for a gene. ex (ABO blood group)
one gene affects the phenotypic expression of another gene. ex: mouse fur color, lab
one phenotype trait is controlled by many genes (skin color)
how can you tell if a trait is polygenic?
the phenotypic trait form a normal distribution (bell-shaped curve)
mendel's 2 laws of inheritance
principle of segregation of allels and principle of independent assortment
principle of segregation of alleles
sexually reproducing, diploid individuals have 2 copies (alleles) for each gene and these alleles separate from each other such that each egg or sperm gets only one allele
principle of indpendent assortment
alleles of one gene assort independently of the alleles at another gene
chromosomes not involved in sex determination
chromosomes that are involved in sexual determination
genes found on sex chromosomes show sex-specific patterns of inheritance
why are sex-linked traits important?
phenotypes are more common in males that females, females can be carriers
genetic mechanisms that equalize the expression of X-linked genes in males and females
why is there dosage compensation?
because females are XX and males are XY
one female X chromosome shuts off leaving one working copy like males, found in all placental mammals
how do female 'calico' and 'tortoiseshell' cats get their mosaic fur colors?
fur color is x-linked. different x alleles make different colors, different cells shut off different x-chromosomes
the ability of an organism with a given phenotype to change its pehnoptye in response to changes in the environment
examples of phenotypic plasticity in humans
height, musculature and skin color
a. DNA is linear molecule
b. consists of 4 nucleotides (A,G,T,C)
c. in any molecule of DNA, A=T and G=C
d. made of 2 strands
e. has a net negative charge
what is different about RNA?
RNA uses the base uracil instead of thymine (U instead of T)
DNA packed tightly into visible chromosomes only during cell division
3 parts of DNA replication
a. strand separation: DNA strands are unzipped by enzyme helicase
b. complementary base pairing: A.G.C,T baes find their complements
c. polymerization- enyme DNA polmerase attaches new bases and re-zips new strands
short piece of RNA that allows DNA polymerase to work
rare because DNA polymerase can correct mistakes most are bad or have little to no effect, good mutations are rare
5 most common types of DNA mutations
1. point mutations: TTATG becomes ATATG
4. duplications- TTATG becomes TTATGTTATG
5. inverstions- TTATG becomes GTATT
what are restriction enzymes?
enzymes from bacteria that cut DNA at specific sequences where the sequence is the same (palindrome) on both strands of DNA
why do some bacteria have restriction enzymes anyways?
they use those enzymes to destroy viral DNA that invavdes them
does transcription occur on both strands of the DNA molecule?
yes but only one one strand at a time
what enzyme makes the messenger RNA (mRNA) molecule?
where in the cell does translation occur?
what is the actual site of translation?
what is a codon?
a group of 3 messenger RNA bases, triplet codon
what does transfer RNA (tRNA) do?
carries amino acids to the ribosome
what is an anticodon?
TRNA complement to the mRNA codon
what is a protein?
strin or chain of amino acids
why do many DNA mutations have no affect on the phenotype?
the third position of the codon can be any base and not change that amino acid
what is a gene?
piece of DNA that codes for a protein with a start and stop codon
what does gene expression mean?
if a gene is expressed it has gone through transcription and translation
does transcription require a primer?
normal cell division. produces two identical diploid cells from one starting diploid cell. makes more body cells
programmed cell death. is what happens to normal cells that are damaged or not functioning properly. if the immune system doesnt get them, many cells will kill themselves
normal control of cell division
1. one cell sends a signaling molecule to another cell
2. signaling molecule binds to a receptor on target cell
3. receptors send cyclin proteins to nucleus
4. cell divides by mitosis
proteins that build up and when they reach a certain threshold, start mitosis
mitosis-promoting factor. protein that initiates mitosis in eukaryotes
genes involved in starting mitosis
mutated proto-oncogenes that cannot control cell division, cancer genes
make proteins that stop cell division and kill cells
example of tumor suppressing genes
BRCA1 and BRCA2: breast cancer alleles. increase risk of BC in males nad females. increase risk of prostate and testicular cancers in males
how do cells lose control of cell division?
mutations in genes that control cell division (mutagens and carcinogens)
abnormal growth of tissue. does not have to cancerous
harmless tumor that do not spread to other tissues examples: warts and moles
non-cancerous tumors of uterus. most common benign tumor in womem
a closed sac with a membrane around it (fluid or air filled)
a collection of pus (dead white blood cells)
cancer (malignant tumor)
aggressive tumors that divide rapidly and spread to other cells and tissues
study of cancer
three characteristics of cancers
1. cells divide and grow abnormally (mitosis out of control)
2. rely on glycolysis for ATP. all energy devoted to cell division
when cancer cells spread to other parts of the body. rough cell surface. cells don't stick together well. travel through interstitial fluid to other body parts and form new tumors
what percent of Americans will develop some form of cancer during their lifetime?
a type of cancer that originates in lymphocytes (usually in lymph nodes)
cancer of blood cells (usually white blood cells) or bone marrow
Skin cancer: basal cell carcinoma
slow growing and most common type of skin cancer
skin cancer: malignant melanoma
an aggressive cancer of melanocytes (skin pigment molecules)
most common cancer worldwide. leading cause is cigarrette smoke
most common cancer among women, U.S. women have highest rate in the world. small, hard, bumpy surfaced lump often no pain associeted with early stages
non cancerous breast lumps
1. cysts: squishy (can move and change in size during menstrual cycle)
2. fibroadenomas- round with smooth surface (hard or soft)
3. psuedolumps- many causes, symptoms: get checked to be sure (eg dead fat tissues, or rib pushing on breast bone)
can men get breast cancer?
yes but 100 times less common in men
some factors that might increase risk of breast cancer
b. cigarette smoke (secondhand smoke)
c. alchohol abuse
e. abnormal circadian rhythm
some factors that might reduce the risk of breast cancer
a. lower age at first birth less than 24 years old
b. having more children 7% lower risk per child
c. breastfeeding (4% lower risk per breastfeeding year)
removal of one or both breasts
removal of ovaries
removal of uterus
most common cancer among men. nearly all men develop it if you live long enough. regular checkups after age 45.
treatment to remove one or both testicles
immune system (vaccination), surgery, radiation, chemotheraphy
immune system cancer treatment
macrophages and natural killer cells can recognize cancer cells and destroy them. vaccination uses antigens that are specific to the cancer cells
removes cancer cells, but ineffective if cancer has metastisized
stops mitosis so good against cancer cells. but damages other cells too. ineffective if metastasis has occurred
relies on a wide range of drugs that find and destroy cancer cells or prevent the formation of supporting tissue (capillaries) which should help kill cancer cells
reproduction without sex. DNA comes from one individual
cell splits into 2 identical cells. Clones. bacteria and some protists
genetically identical individuals grow off other individuals
pieces break off and grow into new individuals
production of offspring from unfertilized eggs
advantages of asexual reproduction
don't have to spend time looking for or fighting for mates
disadvantages of asexual reproduction
very little, if any genetic variation among offspring
DNA copies from 2 different individuals
special cell division. produces haploid gametes from one diploid cell
disadvantages of sexual reproduction
have to find and sometimes compete for a mate
advantages for sexual reproduction
creates a lot of genetic variation among offspring
has working male and female reproductive organs. do not self-fertilize
why not self-fertilize?
no genetic variation
individuals born as one sex but changes to the other sex
born a male, change to female
born a female but changes to a male
genetic gender determination
chromosomes determine gender of offspring
one egg, but a mitosis error creates different populations of cells expressing different genotypes
example of mosaic
blaschko lines- if heterozygous for a skin pigmentation gene, can have large skin patches of different colors. sweat glands too
chromosomes do not segregate equally
half the body is genetically male, half is genetically female
when different cells in the body have different genotypes. cells derived from 2 different eggs taht fused
negative regulatory protein. Y-linked gene that blocks genes on X chromosomes. allows maleness to develop
androgen insensitivity syndrome
mutation in androgen receptor on target cells prevents receiving of male hormones. genetic male (XY) develops as a phenotypic female
environmental gender determination
the environment determines the sex of the offspring
temperature environment determinant
crocodiles, some turtles, some fish, males nad females develop at different nest temps
PCBs, pesticides can feminize male turtles, frogs and gulls
social environment gender determinant
some fish and frogs can change sex if females and males are rare
fusion of egg and sperm
occurs outside female's body, ususally in wet environments
release millions of gametes into the water and hope they find each other
occurs inside female's body
steps of internal fertilization
1.sperm permeates egg coat
2. sperm and egg cell membranes fuse
3. fertilization membrane
4. sperm and egg nucli fuse
5. egg implants into lining of uterus
sac of enzymes that allows the sperm to direct its way to the egg cell membrane
membrane that prevents second sperm from entering egg
can be fraternal, identical or combo
why do some animals have multiple offspring at the same time?
to ensure at least one survives. in good years, all survive, in bad years only one
3 ways to handle a fertilized egg
ovipary, ovovipary, vivipary
eggs laid outside the body
eggs hatch inside body
no egg. young develop inside female
developing embryo is connected to female's body by a placenta and an umbilical cord
young nourished outisde female's body inside a marsupium (pouch)
where are sperm produced?
in the testicles
at puberty paragraph
causes testes to secrete testosterone
causes testes to start sperm production
what do FSH and Testosterone regulate?
what affect do anabolic steroids have on sperm production
excess testosterone causes GnRH, LH and FSH to decrease. testes stop producing sperm and shrink
what is the function of the scrotum
keeps the testes at the best temperature for sperm production
what temperature is best for sperm production
in humans, slightly below body temperature is best. testes can move up and down to regulate temperature
how much fluid per ejaculate?
a teaspoon or two
how many sperm per ejaculate?
300 to 400 million
how fast is an ejaculation
how do sperm find the egg
follow a chemical trail
how long can sperm survive in the vagina
a day or more
w long can sperm survive outside the vagina?
a few minutes
produced in males too, found in semen. may help mates bond
pituitary hormone released in males and females after orgasm. creates feelings of relaxation and satisfaction
can a male control the gender of his children?
yes in a laboratory setting. XY sperm are lighter than XX so sperm can be separated by weight
produce alkaline fluid to reduce acidity in urethra and vagina. produce fluid to lubricate inside and tip of penis. sometimes carries residual sperm (can make a woman pregnant)
produce alkaline fluid to reduce acidity in urethra and vagina and activate sperm swimming. produce hormone prostaglandins. produce 2 enzymes one to clot sperm before ejaculation and one to break it up after ejaculation
produce the sugar fructose to feed swimming sperm. produce prostaglandins
may help stimulate contractions of female reproductive tract
why do prostaglandins help?
help move sperm farther up reproductive tract to the egg
where are eggs produced?
how many eggs does an ovary contain?
at birth around 1 million, at puberty 200,000-400,000. stuck in prophase of meiosis 1
how many eggs released in a lifetime?
how long is the menstrual cycle?
28 days on average
what causes cramps associated with menstrual flow (period)
contractions of uterine muscles to expel the endometrial cells and unfertilized egg
pregnancy induced hypertension
how does the Pill work?
high levels of synthetic estrogen and progesterone fool body into thinking it is pregnant and prevent ovulation. to keep cycle moving, pills taken on days 21-23 have no hormone
what is relationship between body fat and menstruation
females should have at least 17% body fat in order to menstruate regularaly. need to conserve energy
after about age 50, few egg folicles remain, ovaries release of multiple eggs
where does fertilization occur?
in fallopian tubes
how long is the egg in the fallopian tube?
when are women most fertile?
days 10-20 of the cycle
how many pregnancies end in miscarriage
about 1 in 6
lining of uterus where fertilized egg will implant
5-10% of women have this. endometrial cells grow in places other than the uterus. usually painful
fertilized egg implants somewhere besides the uterus
hormone producuced by cells around implanted embryo. causes corpus ludeum to produced large amounts of estrogen and progesterone to the menstrual cycle
what is a pregnancy test?
a quick test to see if HCG is in the urine. if so you are pregnant
what is development
a fertilized egg increases in size and complexity and becomes a reproductive adult
when do identical twins form?
during blastula stage when cells get separated into two distinct groups
does cleavage occur by mitosis or meiois?
how do conjoined twins form?
cells around blasopore separate as in identical twins, but not completely