6.1 Molecular Inheritance Basis

Question 1

Molecular basis of inheritance

Answer 1

Recall Mendel’s experiments with pea plants
in the 1800’s

He proposed a “factor” for each trait that was
passed on from parents to offspring- genes

Question 2

gene

Answer 2

the coding region of DNA that
contains instructions to build a protein

Some fundamental genes are shared by almost
all living organisms

Question 3

DNA packaging

Answer 3

There is a lot of DNA that needs to fit inside every
single cell of an organism

This is accomplished differently in prokaryotes
and eukaryotes

Eukaryotes also have small amounts of DNA in
their mitochondria and chloroplasts, which is
similar in structure to that found in prokaryotes

Question 4

In eukaryotes, DNA coils around ________ proteins
to form complexes that combine to form
___________

Answer 4

histone; chromatin

Question 5

packaging in prokaryotes

Answer 5

DNA in archaea and bacteria is found in
simple loop-shaped chromosomes

They may also contain plasmids, small
accessory loops of DNA

Bacterial DNA is found in an area called the nucleoid

Question 6

genome

Answer 6

The genome consists of the entire set of DNA in
an organism

Humans and many other eukaryotes are diploid –
their chromosomes occur in homologous pairs

Bees, wasps, and ants are haplo-diploid: the
females are diploid, while the males are haploid

Plants can be haploid, diploid, triploid, tetraploid,
hexaploid…

Question 7

meischer

Answer 7

In 1868, he studied
the composition of the
nucleus

Collected pus from
bandages (mostly
WBC’s)

Extracted an
unknown substance
that was acidic and
contained phosphorus

Named it “nuclein”

Question 8

griffith

Answer 8

In 1928, he studied
pneumonia bacteria
(epidemic in Europe at
the end of WWI)

S-strain (smooth) vs.
R-strain (rough)

Injected mice with each
strain and various
combinations

Showed some sort of
hereditary transmission transformation

Question 9

avery, mcleod and mccarty

Answer 9

Based on Griffith’s
findings, they carried
out similar studies in
1944 using
Streptococcus

Possible transforming
substances were DNA,
RNA, and proteins

Results showed that
DNA was the hereditary
substance (went against
current thinking –
proteins)

Question 10

hershey and chase

Answer 10

In 1952, they attempted
to verify if DNA or
protein was the genetic
material

Used bacteriophages
and E. coli bacteria

Labelled radioisotopes
of phosphorus (DNA)
and sulfur (protein) to
determine what part
was being affected
(DNA or protein coat)

Found radioactivity
only inside cells :. DNA

Question 11

chargaff

Answer 11

An organic chemist

Disagreed with
common thinking that
there was an equal
concentration of A, T,
C, and G

In 1950, he discovered
that the bases occur in
definite ratios where A
= T and C = G

Now known as
Chargaff’s Ratios

Question 12

wilkins and franklin

Answer 12

Used X-ray
crystallography to study
shape of DNA molecule

Franklin produced
clearer crystallographs
than Wilkins, whose
work showed a helical
structure

X shape suggested
double helix rotating
clockwise, with
sugar-phosphate
backbone on the outside

Question 13

watson and crick

Answer 13

In 1952, they were
building a variety of
models of DNA to
determine the structure

Wilkins revealed some
of Franklin’s work,
which helped them
realize that a double
helix model fit all of the
known information

Strands must run
anti-parallel

Question 14

Histone

Answer 14

a special protein molecule that is the core around which the DNA strand wraps

Question 15

Plasmid

Answer 15

a small circular section of DNA found in the cytosol of bacteria; replicates independently of the chromosomal DNA

Question 16

Genome

Answer 16

the complete set of an organism’s hereditary information