Human Bio Exam 3

the plasma membrane of the egg is surrounded by an extracellular matrix called the:

zona pellucida

the prescence of this hormone in the blood and urine indicates that a woman is pregnant

HCG

the sex of the fetus can first be distinguished during:

3-4 months

the afterbirth is delievered in which stage of labor

third stage

the SRY gene can be found in both XX males and XY females (t/f)

false - female means no gene

which system develops first in the embryo

nervous

why does blood volume increase in a pregnant individual

to supply nutrients to the placenta and fetus

which of the following chnages is most commonly associated with normal aging in humans

gradual loss of muscle mass

a major focus of fetal development during the third trimester (months 7-9) is:

growth, fat accumulation, and organ maturation

which occurs during stage 3 of labor

the placenta is expelled

alternate forms of a gene having the same position on a pair of chromosomes and affecting the same trait are called______

alleles

if a person has both alleles for the dominant trait, his genotype is represented as:

2 capital letters

a heterozygous brown bull mates with a white cow (brown is dominant) what are the expected phenotype ratios?

50% brown 50% white

how many chromosomes are present in a human gamete after meiosis is completed

23

down syndrome is seen in a person with

extra chromosome 21

during which stage of meiosis does crossing over occur

prophase I

a photograph of cellular chromosomes taken just prior to division and arranged in pairs is called:

karyotype

a centromere is:

point of attachment for for sister chromatids

the type of cellular nuclear division that produces two daughter cells with the same number and kind of chromosomes is called:

mitosis

in which stage are the chromosomes lined up on the equator during mitosis?

metaphase

fertilization

the union of the sperm and egg to form a zygote

steps of fertilization

1. several sperm penetrate the corona radiata (layers of follcular cells)

2. acrosomal enzymes digest a portion of the zona pellucida (outer matrix surrounding egg)

3. the sperm binds to and fuses with the egg’s plasma membrane

4. sperm nucleus enters the egg

5. sperm and egg nucleus will fuse

4 basic processes of development

1. cleavage - cells divide, but don’t increase in size

2. growth - cells enlarge

3. morphogenesis - embryo changes shape

4. differentiation - cells specialize

stages of development

1. pre-embryonic development - 1st week after fertilization

2. embryonic development - 2nd week after fertilization until end of 2nd month

3. fetal development - 3rd month until 9th month

4. development after birth

what happens in pre-embryonic development

1st week after fertilization

clevage, morula, early blastocyst, IMPLANTATION

what happens during embryonic development

2nd week - 2nd month

HGH level rise

3rd week - placenta develops

once placenta fully developed → nervous system develops

what happens during fetal development

3rd month - 9th month

growth in size and weight and organ systems

3rd month - can determine sex of baby

functions of placenta

place for exchange of gasses and nutrients between maternal and fetal blood

also produces HCG, estrogen, and progesterone

SRY gene

determines sex

if present —> male - usually on Y

Birth stages

1. stage 1 - dilation of cervix, tearing of amnion, release of amniotic fluid, expulsion of mucus plug

2. stage 2 - contractions every 1 -2 minutes, expulsion & delievery of newborn, umbilical cord cut

3. stage 3 - delivery of afterbirth (placenta)

chromatin

condensed DNA and proteins

mitosis

happens for growth

1. prophase - chromosomes become visible - nucleus disappears - centrosomes move to opposite poles

2. metaphase (middle) - chromosomes line up at center

3. anaphase (apart) - sister chromatids separate and the centromeres and move towards poles

4. telophase and cytokinesis - chromosomes become chromatin - nucleoli and nuclear envelope reappear - 2 daughter cells

meisosis

for gametes

1. prophase I - homologous chromosomes pair + crossing over

2. metaphase I - homologous pairs line up at equator

3. anaphase I - homologous chromosomes separate to opposite poles

4. telophase I - 2 daughter cells - 23 duplicated chromosomes

5. prohase II - chromosomes condense again

6. metaphase II - chromosomes align at equator

7. anaphase II - sister chromatids seperate to opposite poles

8. telophase II - 4 daughter cells - 23 unduplicated chromosomes

crossing over

exchange of genetic info between non-homologous sister chromatids

occurs during meiosis prophase I

spermoatogenesis

process of making sperm

oogensis

process of making eggs

monsomy

cell only has 1 copy of a chromosome

trisomy

cell has 3 copies of a chromosomes

ex. Down syndrome (chromsome 21)

genotype

genes of an individual

allele

alternate form of a gene

phenotype

physical appearance or outward expression of genotype

examples of autosomal recessive disorders

Tay Sachs disease, cystic fibrosis, phenylketonuria

example of autosomal dominant disorder

huntington disease

polygenic inheritance

trait controlled by several sets of alleles - can be influenced by environmental factors

ex. skin color and height —— himalayan rabbit

incomplete dominance

when heterozygote is intermediate between to homozygotes

ex. curly hair + straight hair = wavy hair

codominance

alleles equally expressed in heterozygote

ex. AB blood

multiple allele inheritance

gene exists in several allelic forms

ex. ABO blood system - A and B alleles dominant over i

sex-linked inheritance

traits controlled by genes on sex chromosmes

most are x-linked bc it has more genes

ex. color blindness, muscular dystrophy, hemophilia

characterisitcs of cancer cells

• lack differentiation

• immortal - not limit to number of times they can divide - telomerase

• no contact inhibition

• reduced need for growth factors (hormone) to grow

telomeres

Repetitive DNA sequences at the ends of chromosomes - shortens every time chromosome divides

telomerase

enzyme that rebuilds telomeres and prevents them from losing its potential to divide

protooneogenes

code for proteins that promote the cell cycle and prevent apoptosis

when it mutates —> oncogenes

tumor suppressor gene

code for proteins taht inhibit the cell cycle and promote apoptosis

when mutated products no longer inhibit the cell cycle or apoptosis

ex. BAx mutation -→ apoptosis less likley

P53 protein

tumor suppressor protein

activates DNA repair enzymes and turns on genes that stop the cell cycle

BRCA 1 gene

codes for DNA repair enzyme from recognizing DNA damage, so cells progress through the cell cycle damaged

breast cancer genes (BRCA 1 and BRCA 2)

mutagen

agent that causes mutations

carcinogen

chemical that causes cancer by being mutagenic

RB gene

tumor suppressor gene

causes retinoblastoma - rare eye cancer

3 stages of cancer development

1. initiation - single cell acquires a mutation allowing repeated cell division

2. promotion - tumor develops and cells undergo additional mutations - to form tumors there must be addtional mutations

3. progression - tumor cells acquire the ability to invade other tissues and become metastatic ——- for a large tumor to grow must have: angiogenesis - the formation of new blood vessels

carcinomas

cancers of epithelial tissues

sarcomas

cancer of muscles and connective tissue — bine and fibrous connective tissue

leukemias

cancers of the blood

lymphomas

cancers of the lymphoid tissues

blastoma

cancers composed of immature cells

diagnosis of cancer

C - change in bowel or bladder habits

A - a sore that doesnt heal

U - unusual bleeding or discharge

T - thickening or lump in breast or elsewhere

I - indigestion or difficulty in swallowing

O - obvious change in wart or mole

N - nagging cough or hoarseness

common cancer treatments

surgery - remove primary tumor

chemotherapy - damages DNA or mess up DNA synthesis in rapidly dividing cells

radiation - ionizing radiation causes chromosomal breakage and cell cycle disruption

immunotherapy

immune system can slow tumor growth

use own immune system to get rid of cancer cells

DNA (deoxyribonucleic acid)

functions: replicates, stores info, mutates to provide genetic variability

structure: double helix, sugar phosphate sides & nucleotide bases

location: nucleus

replication

occurs during S phase of interphase

semi-conservative - each new helix has one original and one new strand

DNA helicase

unzips DNA by breaking H bonds between bases

DNA polymerase

adds new nucleotides using the complementary base pairing rules

DNA ligase

seals breaking in the sugar-phosphate backbone

RNA (ribonucleic acid)

structure: nucleotides with sugar ribose - usually single stranded

3 types: rRNA, tRNA, mRNA

ribosomal RNA (rRNA)

joins with proteins to form the large and small subunits of ribosomes

messenger RNA (mRNA)

carries genetic info from DNA

produced in nucleus, where DNA serves as a template

transfer RNA (tRNA)

transfers amino acids to the ribosomes during protein synthesis

each type carries a specific amino acid

where transcription occurs

nucleus

where translation occurs

cytoplasm

codon

3 base sequence in mRNA

how polypeptides are built

mRNA → read by tRNA (has anticodon) → brings corresponding amino acid to ribosomes → builds polypeptide

translation complex

small and large ribosomal subunits together bound to mRNA,

the ribsomes contain binding sites where individual tRNAs bind w/ mRNA

start and stop codons

start: AUG - methionine

stop: UAA , UAG, UGA

steps of translation

1. initation -mRNA binds

2. elongation - polypeptide lengthens

3. termination

genomics

study of genomes or genes

functional genomics

understanding how the 23000 genes function

comparative genomics

Comparing the human genome to that of an animal’s to understand evolution and gene regulation

gene therapy

insertion of genetic material into human cells to treat a disorder

ex-vivo therapy

stem cells are removed from a person, altered, and then returned

in-vivo therapy

gene directly inserted into an individual through a vector

effects don’t last as long as ex-vivo

recombinant DNA

contains DNA from 2+ sources

vector (ex.plasmid) introduces gene into host cell

DNA sequencing

determines order of nucleotides in DNA

allows reasearchers to identify alleles of disease and create treatments

uses PCR

polymerase chain reaction (PCR)

makes many copies of DNA segement

uses DNA polymerase to copy DNA - stages: denaturization , annealing, and extension

CRISPER (clustered regulatory interspaced short palindrome repeats)

cuts mutated gene or adds gene

uses enzyme: Cas9 - identifies specific nucleotides to be cut

biological evolution

changes in population over time

prokaryotes - 1st true cells

• living things descenced from a common ancestor

• living things adapt to their environment

steps of chemical evolution

gases of primitive atmosphere formed small organic molecules → molecules combined → macromolecules (DNA, RNA, proteins)

• only RNA may have been needed to form the first cells

three vital elements of natural selection

1. variation - individuals vary in physical characteristics that can be passed from generation to generation

2. competition - there must be competition for limited resources, and those better adapted will survive and reproduce

3. adaptation - members of a population with advantageous traits capture more resources and are more likely to reproduce

evidence to support evolution by commmon descent

1. fossils in the fossil record

2. biogeographical evidence

3. anatomical evidence

4. biochemical evidence

fossils

traces of past life that lived at least 10,000 years ago

allow us to trace the descent of particular groups

transitional fossils - have characteristics of 2 different groups

biogeographical evidence

the study of the distribution of plants and animals throughout the world

supports hypothesis that organisms originate in one locale and then may spread out

ex. marsupials

anatomical evidence

explanation for anatomical similarities among living organisms

• homologus structures

• analogus structures

• vestigial structures