Topic 4 Flashcards
nucleus key function
genetic info; site of DNA replication, RNA synthesis, ribosome assembly
nuclear envelope
separates contents of nucleus from cytoplasm
nuclear pore complex
located in nuclear envelope; selective traffic of proteins and RNAs; differs from typical membrane channels
The nuclear envelope consists of which two phospholipid bilayer membranes?
nuclear lamina and nuclear pore complex
nuclear lamina
a fibrous mesh that provides structural support and allows things move along its framework; consist of fibrous proteins called lamins and other proteins
outer nuclear membrane
continuous with ER and enriched with membrane proteins that bind the cytoskeleton
inner nuclear membrane
has proteins that bind the nuclear lamina
Gregor Mendel
deduced the classical principles of genetic on results of pea breeding
Wilhelm Johannsen
gene
gene
an inherited factor that determines a trait
allele
specific type of trait and is one gene copy from each parent
_____ alleles for one gene
any different
genotype
genetic composition of an organism
phenotype
physical appearance of an organism
broad phenotype definition
phenotype= genotype + environment + GE interaction
T.H. Morgan
determined that phenotypic traits are inherited together as linkage groups
number of linkage groups=
number of chromosomes
diploid
two copies of each chromosome
central dogma
states that RNA molecules are synthesized from DNA templates and proteins are synthesized from RNA templates (DNA –> RNA –> proteins)
replication
synthesis of duplicated copy of DNA molecule
Transcription
synthesis of RNA molecule from DNA template
Translation
synthesis of polypeptide chain from mRNA template with help of ribosomes
mRNA
serve as templates for protein synthesis
rRNA
component of ribosomes
tRNA
serves as adaptor molecules that align amino acids along mRNA template
the genetic code
corresponding info from nucleotide triplets called codons that encode individual amino acids
codons
basic units of genetic code
stop codons
UAA, UAG, UGA
AUG
Methionine
Describe the relationship, if any, of organism complexity to genome size and chromosome number
generally…. increased organism complexity means increased genome size, but does not mean more chromosomes!!!
most genes encode…
mRNAs, but some alcove regulatory and structural RNAs
average human gene
a segment of DNA within a chromosome that is expressed to yield a functional product
approximately how many genes in humans
21 000
coding region
portion of a genes DNA/RNA composed of exons
exons
segments of protein-coding sequence
introns
aka, intervening sequences; segments of non-protein coding sequences
introns used to be called..
junk DNA
T/F all coding regions have introns
F
RNA splicing
joining of exons in a precursor mRNA molecule
genes RNA-coding region
Introns (35%), exons only 10%
protein coding sequence
barely 1% is exons that actually contain genetic code sequences that encode proteins
As number of genes increase…. protein-coding sequence…
decreases
genes make up……of entire genome
small portion
phenotypic complexity and genetic complxity
do not rely on each other
chromatin
eukaryotic chromosomal DNA with proteins (twice as much proteins as DNA)
humans genome size
3000 Mb (millions of base pairs)
chromosome number in humans
23
nucleosomes
basic units of chromatin and consist of DNA and histones
histones
small proteins with high proportion of arginine and lysine which facilitate binding to neg. charged DNA sugar-phos. backbone
types of histones
H1, H2A, H2B, H3, H4
nucleosome core particles
contain 147 base pairs of DNA wrapped around an octamer consisting of two molecules each of histones (not H1)
chromatosome
166 bp and H1
H1
a linker histone
euchromatin
decondensed, transcriptionally active interphase chromatin
heterochromatin
highly condensed, transcriptionally inactive chromatin
constitutive heterochromatin
contains DNA that is not transcribed in any cell type (such as some DNA sequences at centromeres)
facultative heterochromatin
contains DNA sequences that are not transcribed in the cell being examined but may be transcribed in other cell types
acetylation
heterochromatin to euchromatin
HAT
adds acetyl groups
HDAC
remove acetyl groups
centromere
region of chromosome that ensures correct distribution of chromosomes; where sister chromatids attach
kinetochore
associated with centromere and where microtubules bind
kinetochore __________- with centromere during interphase
not associated
telomeres
sequences at ends of eukaryotic chromosomes; maintain stability of linear chromosomes and linked to aging and cell reproduction
telomerase
maintain telomeres
telomere DNA sequences
repeats of simple sequence with clusters of G residues on one strand
CENP-A
nucleosomes with CENP-A are incorporated only into centromere; directed by nucleosomes themselves not DNA
Why are CENP-A in nucleosomes important?
for maintaining fidelity of cell division