chapter 8 S Flashcards
what are introns and exons
-introns= parts of DNA that dont get used in making proteins
-exons= useful parts in DNA that get used as templates to make proteins
how does DNA know when to stop or start coding
starts by reading a start codon and stops by reading a stop codon
what does degenerate mean
each amino acid has more than 1 codon
define non overlapping
each base is only read once
give features of RNA
-they are single stranded polymers of RNA nucleotides
-the pentose sugar is always ribose
-bases are adenine, guanine, cytosine and uracil (A,G,C,U)
what are the 3 types of RNA
-transfer (TRNA)
-messenger (MRNA)
-ribosomal (RRNA)
which of the 3 types of RNA contain codons
-MRNA contains codons
-TRNA contains anti codons
-RRNA does not have codons or anticodons
what are the shapes of the 3 types of RNA
-MRNA: single stranded and linear
-TRNA: clover leaf shape
-RRNA: 3D and spherical
what are the functions of the 3 types of RNA
-MRNA carries DNA code to different parts of the cell processing
-TRNA is small and transfers the amino acids from the cytoplasm into the ribosomes
-RRNA forms the ribosomes and serves as the structure for translation
what are the purposes of the 3 types of RNA
-MRNA is transcribed from the DNA of a gene and translates into a polymer of amino acids (a protein)
-TRNA decodes another form of RNA into a protein
-RRNA forms the ribosomes and serves as the structure of translation
what is a gene and what does it do
a specific sequence of DNA bases which codes for a particular protein or functional RNA
give differences between prokaryotic and eukaryotic cells
prokaryotic:
-no histones
-DNA found in cytoplasm
-DNA is circular
-genes do not have introns
Eukaryotic:
-DNA associated with histones
-DNA found in the nucleus
-DNA is linear
-genes can have introns
where are codons transcribed from
DNA
what purpose does a histone serve
the DNA is coiled around the histones to fix its positions. this happens because the positively charged histones attract the negatively charged DNA
why is it important for DNA to coil up in the way it does
to package the DNA into the cells
what happens when DNA supercoils and what process happens before supercoiling
the DNA coils up more or less tightly and chromosomes appear as 2 threads joined by a centromere, which can affect the way the DNA is read. Before supercoiling the DNA wraps around histones
why are telomeres important to chromosomes
they protect the ends of a chromosome from damage
what are the threads of chromosomes called and why
they are called sister chromatids because they are an identical pair of a chromosome
how are homologous pairs formed
sexually producing organisms fuse gametes in order to combine paternal and maternal homologues to form a homologous pair
do homologous pairs always contain the same genes
yes but not always the same alleles
give features of MRNA
-single helix
-complementary strand of 1 DNA strand
-made in nucleus (transcription)
-enters cytoplasm through pores in the nuclear envelope
-acts as a template upon which proteins are built
-easily broken down- exists only while needed to make a given protein
give features of TRNA
-relatively small single stranded molecule
-carries a single amino acid
-the anticodon pairs with the codon on the MRNA
-made in the nucleus but found throughout the cell
what is an anticodon
3 adjacent nucleotides on a molecule of TRNA that is complementary to a codon
give properties about DNA
-double polypeptide chain
-bigger than TRNA and MRNA
-double helix
-pentose sugar is deoxyribose
-bases are AGCT
-mostly found in the nucleus
-quality is constant for all cells of a species except gamete
-chemically very stable
give properties of MRNA
-single polynucleotide chain
-smaller than DNA but bigger than TRNA
-single helix
-pentose sugar is ribose
-bases are AGCU
-manufactured in the nucleus but found throughout the cell
-quality varies from cell to cell with metabolic activity
-less stable than DNA and TRNA individual molecules are usually broken down within cells in a few days
give properties of TRNA
-simple polynucleotide chain
-smallest molecule
-clover shaped
-pentose sugar is ribose
-bases are AGCU
-manufactured in the nucleus but found throughout the cell
-quantity varies from cell to cell with the level of metabolic activity
-chemically more stable than MRNA but less than DNA
