Biology: DNA and Genetic Engineering

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Questions and Answers

What is the function of a bacteriophage?

To transform harmless bacteria into smooth bacteria

To transcribe DNA into RNA

To break down chromatin into nucleosomes

To parasitize a bacterium by infecting it and reproducing inside it (correct)

What is the backbone of DNA composed of?

Nucleotides and histone proteins

RNA and chromosomes

Pyrimidines and purines

Sugar and phosphate groups (correct)

What is the term for the process of genetic material from dead smooth bacteria being transferred to alive harmless bacteria?

Transcription

Replication

Transformation (correct)

Translation

What is the purpose of a nucleosome?

To compact DNA strands Signup and view all the answers

What is the rule for purine and pyrimidine pairing in DNA?

Purine always pairs with pyrimidine Signup and view all the answers

What is the number of hydrogen bonds between C and G in DNA?

3 Signup and view all the answers

What was the purpose of using radioactive isotopes of phosphorus-32 and sulfur-35 in the experiment?

To determine if the genetic material of the bacteriophage was DNA or protein Signup and view all the answers

What was the significance of Chargaff's rules in the discovery of DNA structure?

They showed that the percentages of guanine and cytosine are almost equal in any sample of DNA Signup and view all the answers

What was the key feature of the X-shaped pattern observed by Franklin using x-ray diffraction?

It indicated the presence of nitrogen bases near the center of the molecule Signup and view all the answers

What was the role of Franklin's data in the development of the double helix model?

It helped Watson and Crick to build accurate 3D models of DNA Signup and view all the answers

What was the outcome of the experiment using radioactive isotopes of phosphorus-32 and sulfur-35?

The genetic material of the bacteriophage was found to be DNA Signup and view all the answers

What was the approach used by Watson and Crick to develop the double helix model of DNA?

They built 3D models of DNA using cardboard and wire Signup and view all the answers

What is the main difference between chromatin and chromosomes?

Chromatin is DNA uncoiled, while chromosomes are DNA tightly coiled. Signup and view all the answers

What is the key difference between the chromosomes of bacteria and humans?

Bacteria have one circular chromosome, while humans have 46 linear chromosomes. Signup and view all the answers

What is the function of DNA Polymerase in the process of DNA replication?

To pull apart the DNA helix and add new DNA nucleotides. Signup and view all the answers

What is a sister chromatid made of?

Two double helixes. Signup and view all the answers

What was the conclusion of Avery's experiment in 1944?

DNA is the genetic material. Signup and view all the answers

What did Griffith observe when he mixed heat-killed smooth bacteria with live rough bacteria?

The live bacteria transformed into smooth and disease-causing bacteria. Signup and view all the answers

What was the purpose of Hershey and Chase's experiment in 1952?

To determine whether DNA or proteins are the genetic material. Signup and view all the answers

What is the relationship between the number of centromeres and the number of chromosomes?

The number of centromeres is equal to the number of chromosomes. Signup and view all the answers

Study Notes

DNA Structure and Composition

DNA is made up of nucleic acid polymers, consisting of nucleotides as the building blocks.
A nucleotide is composed of a phosphate group (negatively charged), deoxyribose (sugar), and a nitrogen base (either pyrimidine or purine).
Pyrimidines are smaller nitrogen bases, consisting of C and T.
Purines are larger nitrogen bases, consisting of A and G.

Patterns in DNA

Purine always pairs with pyrimidine.
A pairs with T, and C pairs with G.
The bond between C and G is always 3 hydrogen bonds.
The bond between T and A is always 2 hydrogen bonds.
The backbone of DNA is made up of sugar and phosphate, and is antiparallel on the other side.

Transformation: the process of transferring genetic material from dead smooth bacteria to alive harmless bacteria, transforming it.
Gene: a part of DNA that codes for something specific.
Chromosome: the overall shape of clumped DNA.
Chromatin: strands of compacting DNA.
Nucleosome: a loop of DNA around a histone protein.
Bacteriophage: a virus that parasitizes a bacterium by infecting it and reproducing inside it.

Chromatin and Chromosomes

Chromatin is DNA in its uncoiled state
Chromosomes are DNA in its tightly coiled state
Bacteria have one circular chromosome, while humans have 46 linear chromosomes in a cell
A duplicated chromosome consists of two sister chromatids, which are two identical double helixes

DNA Replication

DNA Polymerase is responsible for pulling apart the DNA helix and adding new DNA nucleotides during replication

Centromeres

The number of centromeres is equal to the number of chromosomes

Griffith's Experiment (1928)

Griffith discovered that a genetic material from a heat-killed disease-causing bacterium could transform a harmless bacterium into a disease-causing one
This transforming factor was later found to be DNA

Avery's Experiment (1944)

Avery isolated and inactivated different molecules (carbohydrates, proteins, lipids, DNA, and RNA) to determine which one was responsible for the transformation
He found that DNA was the transforming factor, and concluded that DNA is the genetic material that stores and transmits genetic information

Hershey and Chase's Experiment (1952)

Hershey and Chase used radioactive isotopes to determine whether the genetic material of a bacteriophage was DNA or protein
They found that the DNA core of the bacteriophage, not the protein coat, was responsible for the genetic material

Chargaff's Rules

The percentages of guanine and cytosine are almost equal in any sample of DNA
The percentages of adenine and thymine are also almost equal in any sample of DNA
Chargaff's rules: A = T and G = C

Franklin's Experiment

Franklin used x-ray diffraction to reveal an X-shaped pattern in DNA, showing that the strands are twisted around each other (helix)
Her findings suggested that the nitrogen bases are near the center of the molecule

Watson and Crick's Model

Watson and Crick built a 3D model of DNA using cardboard and wire, based on Franklin's data
They discovered the double helix structure of DNA

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Description

Test your knowledge of DNA discovery, replication, RNA and protein synthesis, genetic engineering, biotechnology tools, inheritance, and human chromosomes. Topics include transformation, nucleotides, and more.