3.8.2.2 - GENE EXPRESSION Flashcards
one method of transferring RNAi molecules into cells involves combining these molecules with a lipid.
suggest why this increases uptake of RNAi molecules into cells (1)
- phospholipid bilayer
- no need for channel/carrier protein for uptake
testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens.
steroid hormones are hydrophobic.
explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane. (2)
- lipid soluble
- can diffuse through phospholipid bilayer
testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens.
in the cytoplasm, testosterone binds to a specific androgen receptor (AR). an AR is a protein.
suggest and explain why testosterone binds to a specific AR (2)
- has a specific tertiary structure
- structures are complementary
testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens. in the cytoplasm, testosterone binds to a specific androgen receptor (AR). an AR is a protein.
the binding of testosterone to an AR changes the shape of the AR. this AR molecule now enters the nucleus and stimulates gene expression.
suggest how the AR could stimulate gene expression (2)
- AR is a transcription factor
- binds to promoter region on DNA
- stimulates DNA polymerase
suggest how transcription factors can reprogramme cells to form iPS cells (2)
- attach to promoter region
- inhibit/stimulate transcription/RNA polymerase
scientists investigated the role of a protein called CENP-W in mitosis. their method involved cell fractionation and ultracentrifugation.
the scientists began by lysing (breaking open) cells and organelles using a detergent that dissolves lipids in water.
suggest how the detergent releases CENP-W from cells (2)
- cell membranes made from phospholipid
- detergent dissolves membranes/phospholipids
scientists investigated the role of a protein called CENP-W in mitosis. their method involved cell fractionation and ultracentrifugation.
the scientists began by lysing (breaking open) cells and organelles using a detergent that dissolves lipids in water.
explain how ultracentrifugation separates CENP-W from other molecules (2)
- spin supernatant at high speed
- molecules separate depending on density/size
define what is meant by epigenetics (2)
- heritable changes in gene function
- without changes to the base sequence of DNA
explain how increased methylation could lead to cancer (3)
- methyl groups added to tumour suppressor gene
- transcription of tumour suppressor genes is inhibited
- leading to uncontrolled cell division
HIV particles have a specific protein on their surface that binds to a receptor on the plasma membrane of a human cell and allows HIV to enter. this HIV protein is found on the surface of human cells after they have become infected with HIV.
scientists made siRNA to inhibit expression of a specific HIV gene inside a human cell. they attached this siRNA to a carrier molecule.
the flow chart shows what happens when the carrier molecule reaches a human cell infected with HIV.
carrier with siRNA attached binds to HIV protein on plasma membrane of infected cell –> allows carrier with siRNA to enter human cell –> siRNA binds to mRNA transcribed from HIV gene –> mRNA from HIV gene not transcribed
the siRNA would only affect gene expression in cells infected with HIV. suggest two reasons why (4)
- only infected cells have HIV protein on surface
- so carrier only attaches to these cells OR siRNA complementary to one mRNA
- only infected cells contain mRNA of HIV
oestrogen is a hormone that affects transcription. it forms a complex with a receptor in the cytoplasm of target cells.
explain how an activated oestrogen receptor affects the target cell (2)
- binds to promoter region which stimulates RNA polymerase
- increases transcription
oestrogen only affects target cells. explain why oestrogen does not affect other cells in the body (1)
other cells do not have oestrogen receptors
